I have developed a program in Delphy 2007, which shows .AVI files.
Now I want to run MP4 files as well, but cannot achieve it.
TMediaPlayer does not recognize the format by its extension.
Is there an other player available or an upgrade for the one that came with my D2007?

MP4 files require a different codec. I don't know how you would load/enable that with Delphi, but it should not be difficult.

The TMediaPlayer component should be able to play with any codec installed on your computer.

Can you play the file normally using Windows Media Player from Explorer?