Windows xp ram tweak: unlock / use 4gb + ram - up to 64GB download
Explanation: winxp/2000(and newer 32bit) uses maximum approximately 3GB of ram,
even if you have 4GB or more installed - use this to unlock hidden memory.
Note that this is not yet perfect(beta stage), on some systems it may not work perfectly.
Original page with explanation: click
Alternative home page - and html tooldrawer demo: click