as mentioned unless theres something super important , i would re-format windows..
But dont install any "box" spyware removers, they are all pretty well useless and will either slow your computer down or cause it to get infected. ( or wreck your system like yours has been )
Keep your system up to date , dont use firefox because your not solving any problems your just making yourself feel more secure.
Go to
www.antivirus.com every now and then , and keep an eye on exploit news for problems with software you run..
Once you have reformatted copy your running proccesses so you know whats "supposed to be there and whats not " for fuiture reference. also copy the structure of your windows/system32 folder and keep an eye on new files by "sorting by date last modified "
when you fin a file that looks suspicious , type the complete filename into google. if nothing can be found , its prob bad.