WINDOWS 8.1 corrupted,

I want to re-install, it asked product key, I give the PC INFO listed PRODUCT ID, it denied.
 By the way,  it is a lenovo windows 8.0, I updated it into 8.1
 I lost the original product key (CD/DVD etc).
 
The problem is caused by my installing AVG(anti virus software) ? Right now, the control panel cannot be open.
Chrome is still ok, FireFox is down also.

Do you have any good suggestion?