A friend left his laptop at my place to remove spyware from his system. The regular solution I would follow would be to install Spybot S&D, but his system was infected with more spware than what S&D could remove. So after searching for many utlitites on the net I finally found HijackThis, this is like the big daddy of all the spyware applications. You should only use it if you know what you are doing, but it works so well that I had to write about it. It took less than 2 minutes to remove all possible spyware from his system and the performance of his system really went up.
I tried it on my system and cleaned up a few services and statup items that I don't really need and I also saw a marginal performance increase on my system. If you feel you system is slow do give it a try but be sure of what you are removing or better still post the log file on one of the forums and ask for help in removing the spware.