Windows 7: Pawn Shop Computer

As always my friends bring me their treasure laptops to either clean of junk and porn or go for complete re install of the operating system.
I got a call from my friend John who bought a Toshiba laptop from a pawn shop where he works (against my advise). But money rules the world and he got it for a steal.
He gave it to me to clean up mechanically and software.
Problem #1: He didn't have a password
Problem #2: I don't know how to jump the PW, so I suggested a clean install. He still have the license key sticker on the bottom and nothing on the hard drive was anything he wanted, so, we went for it!
All went well till it came to Validation. I used the phone method and read the enormously long string on numbers the PC gave and each element went thru. In the end it said there was an illegal version of Windows being used and validation could not continue. HELP

Have a look through this post Windows Genuine and Activation Issue Posting Instructions

Once you post the MGADiag report, one of our validation experts will be able to help you out.

Do this Windows Genuine and Activation Issue Posting Instructions and we can help you.

Are you sure you used the correct version listed on COA sticker and inputted the correct digits of the Product Key which causes most failures?

It is rare for a COA sticker Key to fail. If you hewed closely to the steps in Clean Reinstall - Factory OEM Windows 7 then it should activate unless its the rarest of cases where the COA sticker itself is not genuine.