Virtual memory is produced by the amount of RAM your PC has + the amount of free disk space you have. Many friends of mine have run into this problem when their children download lots of movies reducing available hard drive space. Ram wise, I like 1 gig at least.
I know alot of machines ship with 512.
You can recover some HD space, by this procedure:
Start>All programs>Accessories>system tools>Disk clean-up
Then another: right click on recycle bin, choose properties, reduce to 3 0r 4%.
Then remove programs YOU DO NOT USE in control panel, add/remove programs. (NOTE:when in doubt keep it)
Then remove movies & videos you don't want or save them to a external drive. External drives are great for saving movies , etc. and are not that expensive.
After you safely remove or move to a external what you do not use. go to system tools again and defragment the drive.