Hopefully it's just something that can be cleaned up with a good virus scan, but sometimes those things can really mess you up. Even if your virus scanner cleans it up it'd still be a good idea to get things set up so that if you do need to format your computer it's not as big of a hassle. Back up files, make sure you've got keys to all your programs, backup your bookmarks, ect. Make sure to not back up things that might be hiding the virus like exe and dll files. Be sure that you're using a good virus scanning program, many of the ones you can find online are actually scams or malware. Check the reviews for it before you get it. I personally really like Spybot - Search and Destroy.