There are plenty of rearm articles for windows 7 around. Unfortunately, it appears they are made for Vista, but are branded for Win7 - basically wont work properly. Problem is that Sysprep does not work the same way as in Vista, and in my case, it was not very reliable. Generalize flag is not welcome through command line, so I ticked the flag in the GUI. Mistake! From the next reboot on, my machine ended up in a endless loop. Actually, Sysprep screwed my system! (see Attach) Point is, you dont need to sysprep your maschine for a rearm at all! A simple: slmgr /rearm with a reboot will do it.