exit programs you are not using, stuff on the taskbar and stuff. alt control delete and remove and process you know it is safe to remove. disable themes and animations
make a RAM disk drive and put your internet cache there or put it in an empty partition
if you have XP(if not, you can stil do this, just starting it is a little more complex)
go to start-run-msconfig, and turn off basicly everything, besides like anti-virus and that stuff. That'll help, because all the backround programs use system rescourses.