Sounds like you were hit with a rogue "anti-spyware" scam. They install spyware onto your computer then try to con you into buying their software to remove it. Whatever you do do not pay them anything. Try these programs.
These are a few FREE programs (which I personally use), which work great together to check whether your computer is infected, if anything is found they will remove the problem files. Make sure to disable your own Anti-virus before installing a new one because it may cause a conflict.
Download the following:
Spybot: Search & Destroy - Application to scan for spyware, adware, hijackers and other malicious software. Make sure to download all of the newest updates before scanning.
http://www.safer-networking.org/en/mirrors/index.html
Windows Defender - Windows Defender is a free program that helps protect your computer against pop-ups, slow performance, and security threats caused by spyware and other unwanted software. Make sure to download all of the newest updates before scanning.
http://www.microsoft.com/athome/security/spyware/software/default.mspx
A Free online Scan you can perform is at Trend Micro’s website. They have an online scanner that works through your internet browser to detect viruses and malware on your computer. http://housecall.trendmicro.com/
AVG Anti-Virus and Anti-Malware Free Edition -http://free.grisoft.com/doc/5390/lng/us/
Make sure to disable your own Anti-virus before installing a new one because it may cause a conflict. Make sure to download all of the newest updates before scanning.
To prevent future problems download SpywareBlaster and PC Tools Firewall Plus. Update them both and make sure to enable all protection.
http://www.javacoolsoftware.com/spywareblaster.html
http://www.pctools.com/firewall/