Thank you to all who offered advice...I think I found the problem (and I got
lucky, too). Tonight I decided to try some troubleshooting, anticipating a
long procedure of removing, swapping and replacing hardware. Well, I began
by removing one of my (3) DIMMS (after letting the computer warm up and
begin blue screening). Lo and behold, I hit the jackpot on my first try! I
removed the DIMM and the computer booted just fine. I let it run for a
couple of hours, including taxing it with DOOM3 and moving some files (did
these to generate some heat and put a good load on the power supply). All
remained stable. I put the DIMM back in, rebooted and instant blue screen!
The memory stick in question is a 1GB DIMM from USModular. Allegedly it has
a lifetime warranty, but I checked the warranty terms and they dictate that
it be returned with the original receipt, original package and original
anti-static bag! (WTF?) I'm going to phone them tomorrow to see how rigid
this policy is. Computer is running fine now using my remaining memory (a
pair of 512MB modules). I installed that DIMM almost exactly a year
ago....interesting that it would fail so suddenly.
Craig