Windows XP Video Decoder Checkup utility is used to check what all MPEG2 codecs are installed in your system and to change / set the defaults preference for the windows media player.
A decoder is a kind of add-on / extra for a media player. Now in windows, we install many software including Nero, WinDVD, PowerDVD and many other player. Now, each player (almost all) has the capability to add their codec to the windows media player. We also can make use of the codec in our programs if we are writing a program, maybe in VB, or VC++ etc.
That is why we are able to play a DVD in windows media player after we install a DVD player.
Most of the time it so happens that after you install many software or codes, a video file may not play in windows media player or Media Center. This happens if you install programs like the "ACE Mega Codecs Pack" or other similar software. This problem can be solved by using this small program.
It lists all the codes installed in you system, with description, whether it is compatible (i mean fully compatible) with windows media player and windows Media Center. You may set the preferred codec as default.
You also get the info about the codec file (DLL or other activex file) so that you can manually register or delete the codec in case of any error, etc.
One point, you need to be an administrator to run this program.