virtual memory

[shashgo]

I sometimes see the following balloon pop up by my status bar:  "You are low on virtual memory.  Windows is increasing ...."  What does this mean, what is virtual memory and how can I avoid this situation? 

It happens on my winXP machine, which is a dell, 512MB RAM, 60GB HD.

[Broni]

Virtual memory, or page file is a part of your hard drive, which computer assigns as semi-RAM for a quick access.
By default, the size of that chunk of a hard drive is controlled by Windows. Depending on Windows needs, virtual memory will be increased, or decreased.
To avoid a pop-up it's better to set fixed value of virtual memory. Usually, it's set as 150% of RAM size - 768MB in your case.

How to: http://support.microsoft.com/kb/308417
See Step 2: Manually manage computer memory
How to manually change the size of the virtual memory paging file

Make sure, you set Initial size, and Maximum size to the same number - 768.