ok, back to Rigacci. You were right after all. I took the dead case to a local computer guy yesterday, and gave him a print out of what I had tried to do (but not any of the suggestions!) He asked how I tested the RAM sticks, and I said I removed them, air dusted the interior, vacuumed up the dust, and then reseated them randomly. He called a couple of hours later and said I was good to go. While picking up the live case, I asked what the problem was so I could see how stupid I was, and he said that he did the usual; i.e. checked hookups, voltage values, changed vid cards, etc. Then he started on the RAM because "it worked once for you, but then when the new message about 'expressgate' coming up, and then everything going down, that seemed a logical place."
He removed all 4 RAM sticks, then tried them out one stick at a time. No joy. Then he started reseating TWO sticks at a time. The third combo got a boot, and he went from there. Cleaned up BIOS, etc. and left 'expressgate disabled' for now, but told me how to enable it if I want it. I asked why the TWO RAM sticks, and he said he remembered that some systems needed to see at least 2GB of RAM before working right. So he tried that... I asked why and he just looked at me for a second, then said 'I'm a techie, not an engineer. I fix'um, I don't design'um'. It cost me a lot less than a new mobo or vid card or the CPU!!!
Thanks for the help here, and I hope this helps someone else out. Thanks again, Rigacci