A few questions before you Format C:
What version of windows?
i have windows 7. The disk I got is for windows vista.
Can you see hte Administrator account at the login screen?
No.
What fake AV is it?
It says it windows 7 2011 anti virus
You if you are somewhat computer savvy try a linux boot disk that has AV loaded. Go here....
http://www.inside-security.de/insert_en.html