Is it a problem to change os with a key code? I am ordering a disc of win 7 pro to go over win 7 ultimate because the key code on there now (on ultimate) says it is not genuine. it was ok in the beginning, now it is bad. I have a repair disc and it won't accept the key on ultimate, says it is not genuine so I am looking at a win 7 pro disc on ebay - says it is a genuine key. Do you see any problems with a new install over 7 ultimate?