For the management of a Vista workstation there is a very useful licensing utility built in, the Windows Software Licensing Management Tool aka “slmgr”
Need to recycle that trial period for another 30 days? Use the -rearm switch before the desktop is locked down by the expiration of the trial. This is reported as working up to 3x or 90 theoretical extended days.
Need to change the product key and re-activate the product? no problem, use a combination of -upk, -ipk, cpky, -ilc, -rilc, -ato, and/or -atp switches :->
Need to see the details of your current license information to learn whether it is retail or open or trial? no problem, use the -dlv switch.
At an elevated CMD window prompt type “slmgr” and wait up to a minute for the Windows Script Host Window to appear as shown below. A tip to get an application such as CMD to run with elevation …hold down the Ctrl+Shift keys as you press the enter key; otherwise you have to right click and select the “run as administrator” option.