If you are using XP ...default setting is to let Windows manage it. You can change this and set it to what you want. Other operating systems allow you to set the min/max
Think of vitual memory as a tempory cache. I don't think adding memory will fix the error. You need to increase the size of the page file.
I can tell you exactly how to do so if I knwe what OS you had
Most are right click on my computer and hit properties
Click on the advanced tab
XP-click on settings under performance
Click on advanced and on the bottom you can change the page file
01 WS6 (sold)