with 2 gb memory starting to get common on some high end system.  I was trying to find what the maximum paging file size.  our old entry we use was 2 x ram memory.  I found out that the maximum size for windows xp is 4GB per paging file with a total of 16 paging files.

http://support.microsoft.com/kb/254649 

A good primer for virtual memory in windows XP is located on this website 

http://aumha.org/win5/a/xpvm.php

 a more complete thought process on virtual memory

http://www.petri.co.il/pagefile_optimization.htm