The License Information can be displayed using the command line License Manager tool built-in Vista’s (slmgr).
Step 1:Open a Command Prompt window and type the command slmgr -dli
The -dli switch stands for “display license information” and shows the last five characters of your license ID.
Assuming you have the product keys written down, you can use these details to see which
key is in use on a given specific machine.
If you want more detailed information, use the -dlv (”display license, verbose”) switch instead.
Hope this helps.