Apples to: Windows Vista, Windows 7, Windows 8 and Windows 8.1
User Level: Beginner to Expert
If you have multiple PC's in your home or business running different versions of Windows and you would like to have them on the same version, you might want to check to make sure you are not using a product key that is already in use. For instance, if you bought 3 copies of Windows 7 Professional, installed one, activated it, but later wanted to upgrade another PC but can't remember which key was used, this quick tip can be very handy.
Click Start, type: cmd
Hit Enter on your keyboard
At the command prompt, type the following command:
slmgr -dli
Hit Enter on your keyboard
A dialog window will appear on screen. This will reveal the partial product key that will give a hint of the product key that is in use. Compare it with the product keys you have and it will confirm which copy is in use. When you are finish, click OK and close the Command Prompt window.
For Windows 8 and Windows 8.1 users:
Press Windows key + X
Click Command Prompt
Alternative ways to quickly launch the command prompt quickly on all versions of Windows:
Press Windows key + R
Type: CMD
Hit Enter on your keyboard
For Windows XP:
Here are four utilities, all of which will may display your product keys if they are still there:
Belarc Advisor: http://www.belarc.com/free_download.html
(It does a good job of providing a wealth of information.)
Also: http://www.magicaljellybean.com/keyfinder.shtml
and: http://www.nirsoft.net/utils/product_cd_key_viewer.html
and RockXP: http://www.majorgeeks.com/download4138.html which has additional features
