http://support.microsoft.com/?scid=kb;en-us;837869
SUMMARY
When you receive an error message about low virtual memory, the program is trying to use more memory (RAM) than is available on the computer. You can adjust the virtual memory settings in Windows to work around this issue, or add more memory to the computer.
WORKAROUND
To work around this issue, you can adjust the virtual memory setting. Follow the steps that are appropriate for your operating system.
Microsoft Windows XP
1. Click Start, and then click Control Panel.
2. Click Performance and Maintenance, and then click System.
3. On the Advanced tab, under Performance, click Settings.
4. On the Advanced tab, under Virtual memory, click Change.
5. Under Drive [Volume Label], click the drive that contains the paging file that you want to change.
6. Under Paging file size for selected drive, click to select the System managed size check box, and then click Set.
7. Click OK three times.
When you are prompted to restart the computer, click Yes.
Assuming you are using XP - there are other instructions for other operating systems in the article.