Fixed probably 10 cases (without having to re-install the OS or lose data) of those viruses in the last year and they're no where near as difficult as they seem. Fixed one called antiviruspower and it's associated shit just last night....
Start with a little app called 'Hijack this' from trend micro, follow the instructions to rename the .exe before running from desktop. Kill the process and delete. Also check C:\Program Files\Common Files\XXXXX as sometimes they're nice and actually leave you an uninstaller
As mentioned run Malware Bytes or similar and finally something like a cracked version of registry mechanic or similar.
As stated already, back up valuable data (and/or image your OS) and make sure your OS and AV software is up to date.