'interesting' Windows sound problems

[flapjack]

Starting last thursday, halfway through an episode of GitS (XviD AC3 encoded) Windows Media Player decided to give up on sound, entirely. WMP will now complain about incompatible file/codec on every sound file, Winamp works fine, Windows itself can still play .wav files, Intervideo WinDVD and the standard DivX player both run movies fine (as in, with sound). In addition, certain games (Morrowind being the only I've tested so far) also seem incapable of playing .mp3 files (Morrowind pops up an error message about not being able to play music.mp3, then shuts down).

Seeing as how it gave up halfway through a movie file, after no changes for over 2 months, I have since used several virus scanners (Norton, AVG and PCCillin's webscanner, all up to date ofcourse) and spyware scanners (Spybot, Adaware and PCCillin's webscanner). Reinstalling WMP and reinstalling the various codecs it seems to have lost haven't produced any results.

The machine on which this is happening is a Fujitsi Siemens Amilo, although it can't be hardware related since Winamp and other programs still produce sound normally. I'd rather like to fix this problem without formatting, because it'll take bloody ages to get it all setup the way it's supposed be then.

Any ideas?