Since no one had any suggestions for me, I reformatted the HDD, reinstalled XP Pro and then BEFORE installing Norton, I loaded the drivers for the video card, ethernet, and Sound. I also downloded all the MS updates for XP Pro. I had already updated the BIOS on the Mobo.
Then I installed Vegas. Everything is now working OK - captured over 16 minutes of video from my camera with no blue screen of death. Looks like it was Norton inteferring during the previous installation, though there were other issues like a SATA controller that seemed to be installed 4 times and would not allow itself to be deleted.