Start with cleaning your HDD. The easiest, fastest and most thorough way to do that is with a program such as Ccleaner.http://www.ccleaner.com/
Scan for malware using the two free programs in the links below.http://www.superantispyware.com/http://www.kaspersky.com/virusscanner
If the two programs above find anything other than "cookies", post their logs back here.
Defragment your HDD
Having a lot of programs running at startup will slow startup and unnecessarily use a lot of computer resources. You only need your firewall and antivirus program in startup. Programs such as media players, Adobe Reader, Windows office programs, Instant Messengers, etc. do not need to run at startup and will make themselves available when needed.
Best to control what programs run at startup by using the settings in each program. There are also free programs that will help you with this such as WinPatrol. http://www.winpatrol.com/
There are many things that can cause a "slow computer". Here is a useful link to help you.http://www.castlecops.com/t175256-Slow_Com...be_malware.html
EDIT: correct spelling
Edited by buddy215, 24 September 2008 - 06:56 AM.