direcx9c and nvidia geforce

ok, since a few days i have the following problems :

shortly after i upgraded my direct x from 9.0 to 9.0c (had to do so for a new game ) my computer started to reboot randomly.

after disabling reboot i got some STOP errors which indicated a graphic card driver problem.
so i upgraded them too.
but still the same errors.
next i booted my conputer with linux and made a full memory scan --- no errors.
then i replaced my GF4 with an old GF2 and again installed the newest drivers on it ---- still the same error, so my GF4 is ok too.

so this is my question : how to get back to an older directx version, or how to get 9.0.c to run propperly ??

p.s. in dx system requirements was a point : need the newest BIOS ... hmmm my BIOS version is 1 year old..... but i dunno where to get an updated and how to do it.... i'd prefer to leave it the way it is....

any help ?

 

A couple of other suggestions to try.

Install the Nvidia reference drivers (if you haven't already?) rather than manufacturer specific drivers.

http://www.nvidia.com/object/winxp_2k_66.93
I prefere these for my Leadtek Ti4200 card, rather than going to the Leadtek site.

If this doesn't help then maybe install an older version from the Nvidia archive site.

http://www.nvidia.com/object/winxp-2k_archive.html