Run a google search for spybot seek and destroy. It is a free download and one of the better ones I have seen. It is best to use multiple programs to get your PC clean, adaware also has a free version which I use in conjunction.
just get a Macintosh and you won't need any of those crappy programs, the new OSX is virtually bulletproof against all kinds of pests you PC people are suffering from.
You will never need to reboot, reformat or re-anything you'd never have to think about you computer or how it works and why it doesn't.
I have ad-aware, and spybot, and one I especially like for cleaning up the registry is Registry First Aid. One does have to be a little careful (alot careful) not to remove required elements in the registry. It can cause a need for a complete reload of the OS. It removes all kinds of unneeded or errors in the registry but the free version only does 10 fixes at a time, requiring multiple runs to clean everything. What it does however is puts a run entry in your registry every time you run it and automatically starts the program. You can either shut it down with the program manager function or remove the start command from your registry. This frees up some memory if you are short of space. I just added a 128M sim and extended my machine's life with the requirements of all the new programs. I run registry first aid frequently so I'm usually under the 10 problem limit. Another quick cleaner is called Crapcleaner or CCleaner. Does a nice job and a quick job of deleting temp internet files etc.
Correction: meant "free resources".
Frigging computer is driving me batty. I bought a movie to play on it and now it tells me no DVD to be found and the freaking drawers don't even slide out. They used to. I would play movies and song albums on it and now it is gone. WTF?