So another tech here that I am good friends with kept stealing shit from my desk. My mouse, phone headset, etc. I lost my patience when he replaced his squeaky chair with my nice one.
So I did some thinking...
He has Win7 installed. Did some googling around and typed this in command line
bcdedit /set removememory 3600
Which left him with only ~400mb of RAM
He's reinstalling Windows right now
It took 10 minutes just to boot up, all eye candy is disabled and "out of memory" errors one after another
Best part is Windows still 'sees' all 4 gigs in system info but only uses ~400 if you look in task manager
To remove it use the command
bcdedit /deletevalue removememory
It applies for Vista or 7 only. If it's XP just edit boot.ini to add "/maxmem=256". Or 128 if you're really pissed off