Do a google search for CWShredder. It's a program that can help get rid of some of the CoolWebSearch (CWS) trojans from porn sites. Also search for HijackThis! but don't fix anything with it without expert help from a site such as
http://newbie.org/helpYou can scan as much as you like, but DO NOT fix without help, or you may get rid of stuff which is vital for your computer.
I use the following to protect my system:
Anti-virus: Sophos Anti-virus
Anti-adware/spyware: Ad-aware SE Personal
Anti-CWS: CWShredder
Anti-everything else: HijackThis!
Hope this helps.
Also, do not use Internet Explorer, since it is very vulnerable to attacks. Use a browser such as Opera or Mozilla Firefox, which can block cookies that download trojans, viruses, spyware, CWS etc.