Hi, my brother has purchased parts and is going to build his computer next week. His old desktop has Windows 7 installed on it and it is an Asus. My question is, Can I install windows 7 onto his new PC with his old CD key? I already have the Windows 7 on a disc. When it asks for a serial key, can he just enter in the one from his old desktop or will it recognize that it is a new computer and not allow it?