Use the "tools" function to get rid of registry errors and speed up your start time.
Revo uninstaller is good for cleaning up the "left behind" files from previous uninstalls.
Check you task manager for stupid shite running in the background and kill whatever is unnecessary. You can do a google search to find out what is and isn't needed.
Also, make sure your plugins are updated: java, swf, etc.
Also, what's your memory size and processor speed? What kinds of applications are you trying to do with the computer?
This post was edited on 1/10 at 1:56 pm