SHERLOCK-The Codec Detective is a freeware application for Windows XP based computers that can scan your hard drive and determine which audio and video codecs are installed on the computer along with their technical details suchas the DLL file name, version, etc.

It can also report codecs which are broken or incorrectly installed. Lastly, you can export the list of codecs installed into a text file which can then be sent to technical support for troubleshooting. The application is very small in size- about 80KB.

Download from here