Reboots upon closing WinMediaplayer or PowerDVD

This strange thing keeps happening from time to time, sometimes weeks in between, sometimes within the same 15 minutes.
The preface:
When a movie (NOT ANY OTHER MEDIA FILE) reaches it's credits, I tend to close the media player like everybody else would. In Windows Mediaplayer (6.4) I don't bother with the STOP button before tapping the little "x" to close the entire thing, in PowerDVD I do before hitting the EXIT.
The thing:
Machine reboots instantly upon closing either media player. NO PROBLEMS WITH THE MOVIE ITSELF OR THE SOFTWARE, PLAYBACK WORKS PERFECTLY, ALL PROGRAMM FUNCTIONS DO.

The Background:
Win2k latest SPs and Updates
ASUS A7N8X-X Nforce 2 Ultra 400
512MB Kingston approved.
Athlon 2600 (no overclocking /tweaking whatsoever)
Windows Media Player 6.4 or 9.0 (tried both on different installations), PowerDVD or WinDVD (-"-), BSPlayer, necessary hand-selected video codecs and filters (no codec packs or such suicide stuff)
Nero Suite 6

What I've heard so far from ppl I told my story:
POSSIBLY Nero ver 6.x.x.x.x Suite, as it contains the highly problematic InCD or Easywrite Reader (...?)
POSSIBLY the sometimes buggy "Web content" preview window in the Win2k Explorer, which shows little thumbnails of pics as well as movies (...?)
POSSIBLY chipset drivers (done, up to date 'n running)
POSSIBLY codec messup (nope as I am a professional in that matter)

 

You forgot, possible directdraw or overlay problem with video, directmedia, or directX drivers. Also, load newest video card drivers.

 

yeah, done all that, new directX, clean video driver reinstall, updated Chipset drivers for the mainboard... it's not the overlay filters /video codecs, as I work too regularily with such software, I know it well enough that I can rule it out.
Haven't had the problem since I posted this thread, I also deinstalled the problematic Nero Suite (InCD Easywrite Reader) AND deactivated the Webcontent in the Explorer. Let's see what time brings.

 

hmmm...
by now I figured out that it has nothing to do with the Nero Suite (while the Suite itself is reported to cause crashes when playing a dvd /cd with video from a disc drive. anyway).

I sniped all unwanted codecs, video and audio, but as I said, this machine runs with this configuration since November last year without a single crash.

what came to my mind is the fact that so far ALL of the movies crashing upon exit are located on the same HDD, namely C:\, a FAT32 partition, which I NEVER used for storing / viewing video, not a single movie so far. As all other drives and partition are NTFS I will now concentrate on relocating the movies there, let's see what happens.