Please try ALL of the steps and procedures in the links below. It may take a while to finish everything but it should help speed your computer up.:

For Windows 2000/XP, ignore the first couple of sentences about checking "resources" in the link below but follow the rest of the procedures including the "Services" links at the bottom.

How To Shut Down Unnecessary Start Up Programs

Because the links for the "Services" are no longer functioning in the link above, use this one:

Services Guide For Windows XP

Next, clean out spyware/adware from the computer by downloading, installing, updating, then running ALL of the free spyware removal programs from the links below:

Ad-Aware