Included in Windows 8 (this tool was first made available in Windows Vista, so this tip will work on earlier versions of Windows) is very useful utility that will help you check the status of activation of your computer:
- From the Start screen, type CMD and press the Enter key
- At the command prompt, type slmgr.vbs /dli and press the Enter key (for a more detailed report run slmgr.vbs /dlv).
Note: Windows 8 supports a new command called: LICENSINGDIAG (e.g. licensingdiag.exe -report c:\output\license_report.xml -log c:\output\license.cab), that generates a report about the activation and registration data on the local computer. This tool appears to be some type of technical support diagnostic tool based on the way it runs.
More information: Frequently Asked Questions About Volume License Keys (Microsoft)