Windows I presume?
1. Get AVG Feee
http://free.avg.com and run checks in both safe mode and normal mode. Do one iteration of both first.
2. Install a rootkit detector and remover (or two or three) and do deep scans with them.
http://www.sophos.com/products/free-...i-rootkit.html
http://technet.microsoft.com/en-us/s.../bb897445.aspx
http://www.google.com/search?hl=en&q...q=f&oq=&aqi=g1
3. Run AVG again in both safe mode and normal mode until both scans show clean
4. Change all passwords.
5. Now fix your HTML files once you have a secured system. If you cannot get it secured you may have to reinstall. Actually reinstalling is the safest thing! Once there is a root/admin level security breach anything but a full reinstall is risky because there is a chance you might miss something.