This version of Windows may not be genuine problems

I've read many posts relating to this problem and nothing seems to work. I bought my machine "used" from a former co-worker whom I can no longer get in contact with. I have no idea if he installed a genuine copy of Windows 7 Ultimate x64. It's been fine for approx. 4 years but now gives me the "This copy of Windows may not be genuine" message. Below is a copy of the MGADiag report. If the copy of...