(I’m trying to sell my MacBook Pro laptop, and haven’t wanted to activate my copy of Vista Ultimate until the last possible moment, hence I wanted to extend my trial license as long as I can. I have found the warning dialog about activation in Vista to be inaccurate by more than a week …).

From a command prompt in Windows, type:

slmgr -xpr

You’ll need to wait for 5-10 seconds …

The answer appears ….

I’ve noticed that in repeated runs of this tool, the specific time the grace period ends shifts from run to run. So, don’t wait until the last possible moment. :)

Remember that if you want to extend the Vista trial license, you need to run this command (as an Administrator):

slmgr -rearm

Wait for the acknowledgement (typically 5-15 seconds), then you must reboot your Vista machine for the extension to take effect.