Blue screen no matter what

[kris.spiers]

Hey there. I'm at the end of my tether here. My girlfriend's computer was riddled with viruses and in the process of removing the old virus software and installing better stuff I've been stuck in a bluescreen loop. I don't have the exact error code right now but looking online it seems like a pretty bad one.
I cannot get into windows at all - not in safe mode, not in any of those. I have made a system repair disc but the repair didn't work.
I was able to back up her files and i was preparing to reinstall Windows.
However ... I can't find her windows product key. Is there a way to get this through cmd prompt? Or is there some software I can use to get this through only command prompt?
Thanks for the help

 

[kris.spiers]

MERGED QUESTION
Question from kris.spiers : "Windows product key"

Hey me again - I should be able to fix a problem with my PC but I can't find the physical product key and I can't boot my computer at all either. Got this %hs bluescreen error that happens no matter what I do.
I can get to the command prompt but all the methods of getting your product key via command prompt are not working.
I am booting off a USB recovery at the moment to get to command prompt