I have several mods running. Most were just fine with previous Morrowind installs.

Right after I defeat Snowy Granius on the bridge, I turn the crank and attempt to enter Arkngthand - game crashes and so does my OS. PC reboots bios and OS. I get no error messages at all.

Windows XP, sp3/ P4 2.3/ Nvidia GeForce FX 256mb/ 1 gig RAM. Clean OS - no other games, anti-virus, or any software installed. Only Morrowind GOTY, Tribunal, then Bloodmoon. Only mod installed that is different from previous successful installs, would be the "Entertainers" Mod.

Have updated my video driver. Disabled all Mods, except Tribunal and Bloodmoon - still cannot enter, as game goes black screen, audio stutters and my computer shuts down and restarts.

Any help, thoughts?

Only advice I can give is to backup your saves and reinstall, since it does sometimes happen that things don't install properly.

Try disabling automatic restarts on STOP errors.
http://pcsupport.about.com/od/tipstricks/ht/disautorestart.htm

Maybe the specific STOP error will help us determine the problem.