Media Player just won't!

Hi, I've got a bit of a problem with one of my bedroom PCs. Trouble is thus:

Windows Media Player (10) won't play anything. At all. I load something up, it just quits itself. I've disabled all the plugins, and still the same problem.

I use Media Player Classic, RealAlternative and QTAlternative, but I use them all on my other PCs as well with no problem. Any help would be great, WMP seems to like setting itself as default player (even though I changed file affinity) so its getting a bit annoying having to wait for it to crash before loading up something in MPC. I would stick with MPC, but as anyone who's ever used it will tell you, it's rubbish for music.

Cheers!

I'm using MP10 already, and tried re-installing a few times. It won't budge. Could it be the 'non-MS-approved' codecs I'm using?