Normally your virtual memory set up is set in a way so that your computer is allocated to certain memory and the rest is used for either your graphics card or something else. You shouldnt play around with the settings unless you are sure you want to.
The only fix for this I can think of is to upgrade your memory. It seems like you have really low memory RAM on your hardware. Get at least 512 or 1 Gig for memory. Its easy to install and its cheaper than just getting a new computer.
Otherwise, I would just close all programs and just keep open what you definitely need. Do not run too many programs on your desktop at the same time...or else you will keep getting that message.
You need to go to your performance settings if you want to change the virtual memory settings, but you could damage your computer that way.
To change virtual settings on XP:
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 market 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. So if you have 128MB of physical memory the formula would be as follows:
128 + 64 = 192MB (64MB being half of 128)
15/ In the Initial Size (MB) dialog box type in 192MB (or whatever figure you have calculated - in our example 192MB)
16/ In the Maximum Size (MB) dialog box type the same figure, i.e., 192MB
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