I am having this exact same problem.
Whenever I play any type of video format (avi, mpg, wmv,
etc.) my computer freezes completely and I can only reboot.
I have the most current version of directX and all of my
Windows Updates are current. I also have the most current
video card drivers I could find (Nvidia doesn't have the
original TNT listed in their drivers download section).
I also have the exact same problem when I try to run iTunes
(I have the most current version and have had this problem
before I installed iTunes)
I've tried un/reinstalling windows, updating drivers to
just about every component in my system, un/reinstalling
the various media players, updating DirectX, etc. Nothing
seems to fix the problem.
I have the following:
Windows XP Professional sp1
NVIDIA Riva TNT, driver v. 2.9.5.8
Intel P3 500mhz
I know my video card is ancient and would be willing to
pick up a newer one if I knew that it'd correct the problem.
--Scott