I only have about 2 minutes but let me say don't go and rush into formatting the disk. Give some things we suggest a try over a week.
I expect you'll have replies by tonight, but I'll come back to you anyhow.
If you haven't already, get adaware and spybot, and run them. They are free and a search on
www.download.com will reveal them. After, get hijack this and post the report.
Further advice will follow
Dan