Here's a easy one to help speed up some systems , mainly those which have 6 or 7 icons in the bottom right of their screen (next to the clock). If those icons are there that means those programs are running in the background whether your using them or not. So go to RUN-MSCONFIG-STARTUP and make a list of any programs with a check next to them, then compare that to the list on this webpage
HERE and try to find ones that don't need to run at startup.
This is a basic thing but I was always surprised when I used to fix computers to see all the crap some peolple have running in the background and then complain about slow performance
Anyway I hope this helps someone.