That sounds very much like what a machine I had went through long ago - the same progression of symptoms that yours has. Mine also started giving errors in NTOSKRNL.EXE if I remember correctly. I tracked it down to either a problem with the memory or with the motherboard. At the time, I didn't have any way to differentiate which was causing the problem. I finally did a system upgrade and swapped out my mainboard, and at the same time I upgraded the memory, so I never did figure out which.

...this would be exactly my luck, to have the mother board go out...

More or less exactly what happened to mine about two weeks ago, though I didn't actually get to read the error message because the computer had been set to reboot on critical error. Turned out to be a motherboard failure, and I'm currently in the process of speccing out a new system.

Do you still get this in Safe Mode? You might be able to work on it in that if you have anything really essential to do on your computer.

Oh, JOY.