Research indicates that even using the SkipRearm registry hack, you can only use this technique 7 times to delay Windows Vista activation. Additionally, you can use slmgr.vbs -rearm three times, making 10 delays in all.
Preliminary experiment, check the activation expiry date with the command: slmgr -xpr
Launch Regedit. (See more details on starting regedit) Navigate to this path:** HKLM\SOFTWARE \Microsoft\Windows NT\CurrentVersion\SL Double-click SkipRearm and change the value to 1.
Note: this registry hack does not make any sense on a machine which has already been activated!
Now remember to run the 30 day extension command: slmgr -rearmRestart the machine.
After it reboots, run slmgr -xpr and check the expiry date.Check the registry setting SkipRearm, slmgr resets the value to zero.