One day my media player stopped playing back video and GraphEdit kept complaining DirectShow Core Components Failed To Initialize. I tried reinstall/updrade the Windows Media Player 11 but that didn't help.
Later I found out that I had to reinstall DirectX to fix it. I tried downloading the DirectX 9.0c Redistributable for Software Developers and ran dxsetup.exe but it completed in a second since it thought my windows already had updated DirectX version. I also tried deleting some registry entries about DirectX, but that didn't help either. Therefore I went to folder where the installation files were and extracted the file dxnt.cab, which gave me a subfolder dxnt. Next I created a system resotre point in case I would need it later.
I then browsed into the newly created dxnt folder and selected all the inf files (sort by type: setup information) in it then right click and click Install on the context menu. It then copied all the driver files from the dxnt folder to %systemroot%\system32 folder and imported necessary changes to the registry. Afterwards, my media player worked again and GraphEdit didn't throw out any more error. However, MediaPortal was still complaining about "VMR9 handler outdated". It seems the above method didn't replace the files being used such as ddraw.dll. Therefore, I did a reinstall of XP service pack 3 to fix it. And MediaPortal was running smoothly afterwards.