,,,, The key is already validated on your computer and can be used again on the same computer.....but more importantly, since volume licenses are only issued to large organizations for their use, you're friend appears to have violated the license agreement and installed the operating system on an outside computer.. If it was legally installed, we would suggest contacting your IT staff who are knowledgeable of methods to fix such issues. It appears that's not the case here.

Hope this helps.