Do you need a wireless adapter for every single computer in your home wireless network?

yes, each must be either wireless-ready, meaning the card is builtin, or it must have a card added, all except if you hardwire using rj45 cable to attach to a pc directly, such as i have on this one..the modem goes thru the router, which is accessed by 2 other laptops in the house along with a pc downstairs with a dlink g520 wireless card in it.

All of these answers are correct. However, I would like to add that wireless is secure if you apply the built-in security features found in all wireless devices in the past years. It is possible to break into these wireless routers but it requires skill and unless you are transmiting sensitive information it is no real worry.

In contrast, a RJ-45 cable can connect it directly to most router devices, but it will restrict the range of the computer.

But simply, every device that will communicate with the wireless router will require a wireless card or USB wireless device.

Good luck and safe computing.

Not me, wireless things make it easier for people to spy on you - it's bad enough when I use my laptop at work, I have to encrypt everything before it goes into the mainframe to get decrypted - it slows everything way down.

Unless you have a cable to connect to your computer from where ever like a Router to where ever the Internet comes from, yes. The cable is instead of having a wireless connector, in fact i would advise anyone using Wireless to use Cable if you can as it it Faster and Safer.

Each desktop/laptop/netbook must have a wireless card built in to enable it to receive/transmit a radio signal.