Here is a new wrinkle.  When in SAFE mode, there is no problem.  This seems to rule out the power supply and video card issues.  However, a full scan from Norton Anti-virus revealed no issues there as well.

The registry has been cleaned out and anti-spyware run. 

It could be a corrupt file in some non-vital (not loaded in safe mode) area of windows, but how to narrow it down?  A re-load of the OS would result in the loss of non-replaceable software that has been lost over the years. 

Any thoughts on ways to narrow down the culprit?