It means your memory is low and need to delete some stuff or increase your memory by other ways.

Windows uses virtual memory as a way to "boost ram". It's using part of your hard drive to simulate ram. It's slower than ram itself because it has to read write all the time. Solutions: 1/ More ram 2/ Disable or prevent useless programs from running in the background 3/ Adjust the swap file size. In XP, the method is as follows 1/ Click the Start button 2/ From the Start menu Click Control Panel 3/ When the Control Panel window opens click the System Icon 4/ In the System Properties window click the Advanced tab 5/ The top section of the Advanced tab window is marked Performance. 6/ Click the Settings button 7/ The Performance Options window opens 8/ Click the Advanced tab 9/ At the bottom of the window you will see a section marked 'Virtual Memory' Click the Change button 10/ In the next window your main C: drive should already be highlighted. If it isn't then right click on it with your mouse to highlight it. 11/ Now look just below the Drive section. You will see a section marked 'Paging File for selected drive.' 12/ Right click on the radio button next to the Custom size to enable this option 13/The Custom Size dialog boxes now become available for use 14/ The normal formula for virtual memory is 1.5 times that of your physical memory. 15/ In the Initial Size (MB) dialog box type in whatever figure you have calculated 16/ In the Maximum Size (MB) dialog box type the same figure 17/ Now click the Set button to save your new settings 18/ Next click OK 19/ In the next screen click the Apply button followed by OK 20/ You should now be back at the System Properties window. Click OK to Exit The easiest to implement is always going to be stopping things like messenger from starting with windows etc. Adding more ram is next. Win XP for example, wants to have about 350 megs of ram to be really happy.That's just for XP itself, nothing else. If you have to have all of those win start up apps going, then this route will keep everything happy providing you have room for more ram and the cash. The last one is managing your own page file, but I'd only go that route if I couldn't do the rest of the above. Windows actually does a decent job of managing it automatically but I'll agree there are times when you just need to give it a boot in the pants and the reason I included instructions on it.

I will try to keep this simple and relatively free of technical jargon. Virtual memory uses hard drive space as memory. Based on your comments, you have more than enough free space available on your system and have likely not changed the virtual memory settings; only geeks do that. Here is one possible problem - Is that free space on your main (C:) partition/drive, or on a different one? If not, rearrange stuff until it is. If so, wade through scubabob's answer. There is no way around it if that's the case. One other DEFINITE problem is a lack of memory. The more real memory you have, the less often you use virtual memory. By itself this will speed your PC up immensely. If you are running less than 256 MB of real memory with Windows XP, you will run slower than death. How much memory do you have?

Forgive me for suggesting this, but given your level of experience and understanding of computers (based on your responses to the answers provided so far), I have a suggestion. You should try to find yourself a local course or seminar on computer basics - one that teaches things like RAM and hard disk and virtual memory, etc. Meanwhile, I have only one thing to add to the fine advice you have been given so far - you want to discover what processes are running on your PC and investigate what they are. Right click on your task bar and select the Task Manager. Choose the Processes tab and begin investigating what programs are running on your PC. Of course, you will have a much more productive time of this if you get some experienced help. In answer to your original question though, no - it is not fatal, it's just your computer complaining that it has too much to do and too few resources to handle it. It sounds like your system needs a software tune-up.