If your computer is saying that your virtual memory is low, then either: Your virtual memory settings have been set too low, you have too many programs open, or there are unwanted programs open that are hogging your memory.

Get CCleaner from Free software downloads and software reviews - CNET Download.com and run that to clear some space on your hard disk. Do the swap file mod above.

See also:
Windows XP Low on Virtual Memory | Techvy