Ouch. Well you could download and run Spybot Search & Destroy (update it before running a scan), and also an online virus scan such as
http://housecall.trendmicro.com/uk/...or this one from BitDefender:
http://www.bitdefender.com/scan8/ie.html
But really, with a system that sounds that compromised I'd reinstall the OS personally.
What anti-virus/anti-spyware/anti-malware software do you currently have on your PC?