For me, an ounce of prevention is worth a pound of cure. As it stands only Microsoft Windows systems are plagued with viruses, spyware, adware and other such nasties. Whilst not immune, other popular operating systems such as Linux and Mac OS X are not plagued with viruses in the same way and it is extremely rare to even hear about a virus - in fact, point me to one single current Linux virus if you can! In contrast, Windows has hundreds of new pieces of malware each day. So, if I'm looking to be safe on line I simply use a Linux system (or an OpenBSD system, or a Solaris system). Even better still, a Linux Live CD on a system with no hard disk drive could never have a permanent infection, even if a Linux virus did exist. You may have a mix of operating systems at your disposal, in which case you'd want software that work on Mac OS X, Linux and Windows. In this area, Sophos antivirus is a great choice - its multi-os, it protects and cleans, and it handles various types of malware.

Spybot Search & Destroy is good and free

Ask 12 people and you'll get 12 answers, but there are a few reliable programs out there - some free - most not. I have no issues with AVG, Avira, Avast, Kaspersky, Sophos and Bitdefender. I avoid McAfee and Norton not because they are garbage, but because they tend to bog the system down considerably. Your mileage may vary.

Zone Alarm

As Karl says there are many answers to your question, so I will offer my really long answer as normal. It is what I use myself and many find them useful. SIMPLE STEPS TO DOWNLOADING VIRUS & SPYWARE PROTECTION (& steps for protecting PC) For XP NEWEST AVG 8.0 BOTH ANTI-VIRUS & ANTI-SPYWARE (for those running Vista you must have all updates done plus SP1 to use) http://free.grisoft.com/ww.download?prd=afe AVG anti FOR SPYWARE, MALWARE, ROOTKITS http://www.filehippo.com/download_avg_antispyware/ Click on the right hand side of page where it says download latest version 11.84MB When next page opens watch for yellow bar at top which you may have to click to allow download to start, click and choose save to desktop. Then open from there. AVG Vcleaner-cleans 704 viruses and variants http://www.scanwith.com/download/AVG_Vcleaner.htm Now for your next layer of protection download the following also but remember you can only run one program at a time, but each of these will fine things the other didn’t. Spybot search & destroy found at www.safer-networking.org DOWNLOAD SPYBOT SEARCH & DESTROY ONCE YOU HAVE TYPED www.safer-networking.org IN THE YAHOO OR GOOGLE SEARCH BAR (you may see yahoo or google asking if you mean .com instead of .org it is suppose to be .org at the end of web site) 1. IT WILL SAY HOME OF: : The home of Spybot-S&D! 2. UNDER THIS YOU WILL SEE THE WORDS: Download. Home of SpyBot-S&D, and 6 different languages. Simply click on the language of your choice for example; ENGLISH 3. THIS IS THE HOME PAGE, LOOK DOWN AND FIND UNDER PRODUCTS, SEE 1.6.0 AND RIGHT UNDER PRODUCTS WORD YOU SEE PICTURE OF S&D CLICK IT, THIS IS ALL SAME LINE. 4. NEXT PAGE SAYS OVERVIEW, SCROLL DOWN AND SEE AREA, CLICK FIRST DOWNLOAD. 5. THESE ARE THE MIRROR SITES, THERE ARE 11 TO CHOOSE FROM, Safer-Networking Ltd. #1 ON THESE CLICK DOWNLOAD AND BOX OPENS, CHOOSE WHERE YOU Safer-Networking Ltd. #2 GOING TO SAVE FILE TO, DESKTOP, MY DOCUMENTS AND OPEN AND Safer-Networking Ltd. #3 AND RUN FROM THERE FILE IS 14.3MB ( only 2 steps here) (these are always my first choice as they usually work well first time) BN FileForum (This is my second choice just a little harder to use, more steps) PAGE WILL OPEN, (BLUE DOWNLOAD NOW 14,380 KB) CLICK blue / NEW PAGE OPENS. MAY HAVE TO CLICK YELLOW BAR AT TOP OF PAGE TO ALLOW FILE TO DOWNLOAD ON THIS ONE, AND THEN DOWNLOAD WILL BEGIN 6. BOX OPENS CHOOSE SAVE AND DO SO TO YOUR DESKTOP OR TO YOUR DOCUMENT FILE AND OPEN AND RUN FROM THERE FILE IS 14.3MB Superantispyware found at http://superantispyware.com SUPERANTISPYWARE DOWNLOAD ONCE YOU HAVE TYPED http://superantispyware.com YOUR SEARCH BAR IN YAHOO YOU WILL SEE: SuperAntiSpyware.com- (AntiAdware, AntiSpyware, AntiMalware) CLICK 1.LOOK FOR BIG BLUE BOX ON THE LEFT SIDE OF THE PAGE SAYS DOWNLOAD FREE VERSION HOME USERS - CLICK 2. NEXT PAGE SCROLL DOWN, AGAIN LOOK FOR THE BIG BLUE BOX SAYS DOWNLOAD FREE VERSION HOME USERS - CLICK Next page opens and again click the blue box that says download FREE version home users. 3. NEXT PAGE DOWNLOAD SHOULD START AUTOMATICALLY (6.16MB), Version: 4.15.1000 ****NOTE (if it doesn’t start at once look at the top of the page for a light yellow bar, its basically a security bar, click and choose allow, it usually has to do with Active X) If still does not open look on the page under the words Download progress: If the download does not begin shortly please (click here is in blue) Click it 4. DO SO AND A BOX OPENS, SAVE TO DESKTOP OR MY DOCUMENTS, OPEN AND RUN FROM THERE And finally go to this web site for this program to clean up your internet history, cookies, browser history, recycle bin, IE Explorer, etc all the boxes can be preset and basically in 4 steps you can clean computer. It does so well that disc clean usually only will find 32-100MB after its done http://www.snapfiles.com go to the freeware section, look for Internet Cleanup, then look for the software called IE Privacy Keeper IE PRIVACY KEEPER DOWNLOAD WHEN YOU TYPE www.snapfiles.com IN YOUR YAHOO OR GOOGLE SEARCH BOX THIS IS WHAT YOU WILL SEE WHEN IT OPENS Snapfiles - software reviews, download freeware and trial programs - CLICK 1. WHEN THE PAGE OPENS LOOK FOR A TAB AT THE TOP OF THE PAGE THAT SAYS FREEWARE - CLICK 2. WHEN PAGE OPENS SCROLL DOWN AND FIND INTERNET CLEANUP TOOLS - CLICK 3. WHEN PAGE OPENS SCROLL DOWN TILL YOU SEE THE PROGRAM SHOULD BE LIKE ABOUT THE 14TH ONE DOWN - CLICK THE BLUE DOWNLOAD BUTTON FILE SIZE IS 1128kb 4. NEXT PAGE OPENS IF DOWNLOAD DOESN’T START LOOK FOR A LIGHT YELLOW BAR AT THE TOP OF THE PAGE, CLICK THE OPTION TO ALLOW TO OPEN, USUALLY HAS TO DO WITH ACTIVE X ***NOTE If for some reason still doesn’t start click the blue words click here they are in the middle of the page in tan box. 5. WHEN THE BOX OPENS SAVE TO DESKTOP OR MY DOCUMENTS, OPEN AND RUN FROM THERE. Last but not least do Defrag at least 2-4 times in a row even if program says not needed, as XP Defrag program isn’t the best and needs to be run more often. GLARY UTILITIES DOWNLOAD GO TO www.pcworld.com 1. WHEN PAGE OPENS , LOOK AT THE TOP OF PAGE WHERE IT SAYS DOWNLOADS CLICK 2. NOW TYPE IN THE SEARCH (blue) BOX - REGISTRY REPAIR PROGRAMS - CLICK AND GO 3. LIST WILL OPEN, SELECT THE HALF WAY DOWN PAGE WITH GREEN ARROW - GLARY REGISTRY REPAIR (ITS FREE) CLICK IT 4.. NEXT PAGE, YOU WILL SEE A RED ARROW AND DOWNLOAD NOW IN BLUE WORDS - CLICK 1.30MB 5.. NEXT PAGE BLUE BOX DOWNLOAD FREE REGISTRY REPAIR NOW- YOU CAN CLICK HERE BUT REAL SLOW (works on 98, XP, ME, 2000, 2003, Vista) just not 64 bit supported 6.. For a faster download click where it says - mirror here 7.. NEXT PAGE IF IT DOES NOT START IN 5 SEC LOOK FOR A SECURITY BAR, WHICH IS LIGHT YELLOW AT TOP OF PAGE, CLICK THE OPTION TO ALLOW IF FOR SOME REASON IT STILL DOESN’T USE THIS OPTION: LOOK FOR THE LINE THAT READS CLICK HERE IF IT DOES NOT 8.. BOX OPENS SAVE TO DESKTOP OR TO MY DOCUMENTS AND OPEN AND RUN FROM THERE http://www.snapfiles.com/Freeware/ SPAM Type in Spam in the search box in the upper right hand corner- new page opens with a list of 5 page, on page 3 you should find this program Spamihilator (2000/XP/2003/Vista 1.08MB) click download, new page opens, watch for yellow bar at top as you may have to click to allow to start download. Click save to desktop or my documents. Then click run to open. or to http://www.snapfiles.com and to their freeware section to find other software also. (can only run one virus program at a time on a PC but you may have as many spyware programs as you wish as long as you run only one at a time, and only one firewall) A GREAT FREE ONE IS ZONE ALARM FOUND AT www.snapfiles.com under the freeware section, personal firewalls. Also found at snap files, are Defragmentation Tools - there are several programs to choose from I recommend you check them out as the one that comes with XP does not always do the best job. Another little great tool for you is go to Google or Yahoo : One of the best pieces of FREE software there is today that will show you what is on your computer is known as: Belarc once it is downloaded you simply run and time you wish to see what is installed on your PC, from OS to Model, hardware, software, hot fix’s and the Keys to software on PC. This makes it a valuable program in that you can run it every so often and print off and save for you keys if for no other reason. *** Note: It is wise to only run one virus program at a one time but run as many spyware as you like, only run them one at a time, other wise they will conflict with each other, it is good to have more than one as each will find some thing the other did not. Unistall any other program as they may conflict such as Norton,MacAfee etc. The only one this list that runs in safemode F8 is AVG anti-spyware, which does work great in safemode. Also wise thing to do is to run the virus & spyware program once without internet connection and then again with internet, as some times the virus will try to block program other wise when internet is running. This list has been drawn up by me and designed by me and is not copyed from anywhere as it has been suggested, please feel free to use as much as you like, and I hope it helps in some way. G_tech

AVG is pretty good, though if you mean downloadable program, try Spybot: Search and Destroy or Ad-aware. Good stuff!

Trend Micro

AVG does it for me.

AVG to me is the best antivirus, and as G_tech said, the latest version has both antivirus and antispyware protection. Also, as it is mentioned in the previous answers, Spybot Search and Distory is also great when it comes to spyware issue. Finally, Ad-aware is also a program to keep in mind when spyware problems occure.

Norton works for me.

Nod32 Norton is tooooooooo heavy on startup

Node 32

My standard rant ... Many threats are stealthfully downloaded and run malicious programs from remote Zombie servers, surrendering control of your system to cyber-criminals. Among other things, threats may copy themselves into your operating system folders, alter your Startup routines, and/or hijack your browser. Most serious threats will defeat whatever anti-virus and anti-spyware applications you are using, giving the impression that you are completely "safe" when you are not! There are many virus and Trojan removal tools on my Security page, including HiJackThis! (see warning below) Before you do any repairs, disable System Restore to prevent re-infection when you reboot. If you are having difficulty running any of the online scans, please reboot in Safe Mode. Once you have run at least three different online anti-threat scans from my Internet Security page, and have determined that your system has been cleared of threats, you may re-enable System Restore. I suggest that you begin with Windows Live Safety Scan (recommended), BitDefender, Ewido/AVG, Kaspersky, or Panda ActiveScan, among fifteen online threat scanners from my Internet Security page ... http://SecorConsulting.net/pages/security.html You may also use this new Rootkit Analyzer by the good folks that brought you SpyBot … http://forums.spybot.info/showthread.php?t=24185 … or this one … http://www.gmer.net/index.php Furthermore, Prevx CSI as another quick check that identifies many common threats ... http://www.prevx.com/ You may need to remove any previously installed anti-virus, anti-spyware, and registry cleaning applications that you are currently using. One or more may already be seriously compromised or corrupted. I recommend that you download and install Crap Cleaner for housekeeping (please un-check the Yahoo toolbar option during installation). Please check for Updates, run an analysis and clean all drives of temp files, followed by a Registry scan and fix. I clean out temp files daily, check the registry daily, and check for updates monthly … http://www.ccleaner.com/ Install SpywareBlaster to protect your browser and HOSTS file from exploitation. Check for updates, then "protect all" (update monthly) ... http://www.javacoolsoftware.com/ REMEMBER, THERE IS NO SINGLE "BEST" ANTI-THREAT APPLICATION THAT IS 100% INFALLIBLE! Please keep in mind that VirusTotal statistics (http://www.virustotal.com/estadisticas.html) indicate that NEARLY ALL of tens of thousands of suspect files submitted each week go undetected by at least one of the thirty most popular anti-threat applications! A few may come close, but there are no "silver bullets" anywhere on the horizon. Any software publisher that claims otherwise is a LIAR! Please install at least one of the following anti-threat applications. Each has their own strong and weak points, but they are all among the best. Check for updates immediately after installation and update frequently thereafter (daily is preferred) Avast! - http://www.avast.com/ AVG - http://www.grisoft.com/ (anti-virus AND ewido anti-spyware) Avira - http://www.avira.com/ BitDefender – http://www.bitdefender.com/ CA Antivirus - http://www.ca.com/ F-Secure - http://www.f-secure.com/ Kaspersky - http://usa.kaspersky.com/ NOD32 - http://www.eset.com/ Norman – http://www.norman.com/ (definitely NOT Norton!) Panda Antivirus - http://www.pandasoftware.com Prevx – http://www.prevx.com/ Sophos - http://www.sophos.com/ TrendMicro - http://www.trendmicro.com/ Windows Live OneCare - http://onecare.live.com/ ( Most of these anti-threat application developers are available from links on my Security page. Most offer FREE or trial software, and many "play well together", should you intend to install more than one anti-threat tool (recommended). Also, to protect your browser form future hijackings please install ... XPL/AVG LinkScanner ... http://www.explabs.com/downloads/ or McAfee SiteAdvisor ... http://www.siteadvisor.com/download/ie.html If you have an IT background you will find HiJackThis! from my Security page an invaluable tool to track down and remove stubborn malware. Use the convenient online analyzer or upload your HJT! log to any appropriate HJT! forum for assistance. CAUTION: If you do not know your way around the Windows operating system, please do not attempt to use HJT!, as you may render your system unusable! Now let’s alter your unsafe Internet practices. Change your mail reader (e.g., Outlook) to accept only plain ASCII text emails and never open attachments from unknown sources. Avoid all file/music/video sharing sites. Maintain a very small IM community (if you must), and become realistically “paranoid”. “They” are indeed out to get you! Make certain that your Windows firewall (or other software firewall) is active and FULLY STEALTHED. Remember that a "closed" port is every bit as visible to the outside world as an "open" port. I prefer using both hardware and software firewalls. Here are a few good software firewalls … Ashampoo Firewall http://www2.ashampoo.com/webcache/html/1/product_2_0050__.htm Comodo Firewall http://www.personalfirewall.comodo.com/index.html Jetico Firewall http://www.jetico.com/jpf2.htm Kerio Winroute Firewall http://www.kerio.com/kwf_home.html OnlineArmor Firewall http://www.online-armor.com/downloads.html Outpost Firewall http://www.agnitum.com/products/outpostfree/ PortsLock Firewall http://www.devicelock.com/pl/download.html Sunbelt Kerio Firewall http://www.sunbelt-software.com/Home-Home-Office/Sunbelt-Personal-Firewall/ ZoneAlarm Firewall http://www.zonealarm.com/store/content/catalog/products/sku_list_za.jsp Avoid the use of ALL "no name" anti-threat and registry cleaning applications. THEY CAN AND WILL COMPROMISE YOUR SYSTEM! All those who are careless and harbor any manner of threat (due their lack of diligence or general apathy) should include themselves as part of the problem. They are a public menace. Please avoid all contact with these morons, otherwise they will re-infect your system! The best of luck in fighting the good fight! My Internet Security page ... http://SecorConsulting.net/pages/security.html My ID Theft page ... http://SecorConsulting.net/pages/identity.html My XP security “hardening” page (there is no Vista direct equivalency at this time)... http://SecorConsutling.net/pages/benchmark.html

Intego's virusbarrier.

According to PC World's best anti-virus test it's "BitDefender 9 Standard" http://www.pcworld.com/article/124475/top_antivirus_software.html

However it's Kaspersky this year. Drawbacks are Kaspersky is expense, $50+ a year.

defender pro 5in1

Pardon.

Norton antivirus.

AdAware works fine with me. Its free and gets rid of almost everything. Note here that no single software will get rid of everything, so you should have more than one, but in my experience AdAware has always done the job.