In Vista, it is good to have a feature to keep a track of how many days ticking you have until you activate your copy of Vista.
here it is how to view the activation status:
Open a command prompt,
type slmgr -xpr
and press Enter to see whether your installation is activated or not.
The details appear in a separate information box (Have Patience it takes some time) , not in the Command Prompt window.
The information you see will tell you whether your copy is activated.
If it’s not, you’ll see the deadline when you’re required to activate.
Hope this helps.