Vista PID Checker is a command-line utility for Windows, used to check the validity and decode information about Product Keys for Windows Vista. It uses Vista's own mechanisms to do this.

It depends on two files every Vista owner has on his PC, eg:

pidgenx.dll
This does the grunt work - decodes the key (if valid).
Can be located on a vista system at:
%windir%\system32\pidgenx.dll

pkeyconfig.xrm-ms
Contains the data that pidgenx.dll uses - key ranges, public keys, etc.
Can be located on a vista system at:
%windir%\system32\licensing\pkeyconfig\pkeyconfig.xrm-ms
(Were %windir% is typically c:windows)

These files need to be in the working directory (usually the same directory) as the executable. Note that these files can be copied from a Vista system, to a non-Vista system (for example, Windows XP) and the executable will still check Vista Product Keys, assuming it can load these files.

Usage
The application will attempt to decode any key to use as a command line arguments. If none are specified, it will read from stdin. This will allow you to run batch jobs, checking product keys. For example: 

VistaPID.exe XXXXX-XXXXX-XXXXX-XXXXX-XXXXX 

VistaPID.exe < keys.txt 

For more help about running the application, open up a command prompt in the directory you've extracted the application to, and run:
VistaPID.exe --help

Website
http://www.theunfocused.net/wiki/index.php?title=Vista_PID_Checker