If your drives have been infected...forget about any anti virus software...here's what u do...trust me it works better than any anti virus software i know....
1. Backup any important files from C drive to any other drive
2. Format C drive
3. Install OS
4. Once the installation has finished, (follow this instruction to the letter) open "My Computer"
5. Go to folder options and select "Show hidden files and folders" and untick option "Hide extension for known file types"
6. Go to the address bar and select any drive,example E: DRIVE
7. Your drive is now opened through the address bar. Look for any suspicious files like "autorun.inf","New Folder.exe" etc., DO NOT DOUBLE CLICK ON ANY OF THESE FILES..... JUST DELETE THEM PERMANENTLY.
8. Once you have finished upto step 7, DO NOT CLICK "BACK", "FORWARD" or "UP"
9. Once you have finished upto step 7 for a drive, repeat from step 6 to 8 for all other drives.
Trust me this works better than any anti virus software that exists. I found this method on my own through sheer experience with all kinds of virus !