I have an official MS COA label that I found with a dead tower I tried to repair. The OS was not identified. The label had been cut. Is there anyway I can tell which OS , XP, VISTA, ect this COA represents? In the past I have used my DELL cd to load XP onto HPs and others. As long as the host tower was also XP as indicated on the COA I could use THAT key to activate the OS. I reused that key several times on various non DELLS. Any help in identifying the OS that this COA represents would be helpful.