In response to your theories Russ,

1. Power supply drop outs - since it would freeze at different stages of 
startup, could there be momentary drops in one or more of the PS 
voltages?  The PS tests ok now, but maybe under load it drops out 
occasionally.

- Yeah, well, this was my first thought too.  I work for a franchise called Batteries Plus so voltage is a daily thing for me.  I would say something is wrong if each of the power connecters weren't always reading a consistant 12 volts, but they are all right on, everytime I check.  Not 11.9, or 12.1, 12 on the nose.  And again, the fan on the NX6600 was working, power is flowing through the thing.

2. Some driver conflict - maybe since I can't really tell what drivers 
load when during boot.  But the fatal failure was during flashing the 
BIOS from a bootable floppy when there aren't many drivers loaded.

- Again, always possible.  But it was working just fine before I tried to install the NX6600.  I didn't load any of its software so there are no new drivers installed.  I would assume there could be a problem with the new card, but with the old one everything should be smooth.

3. Some firmware failure in the BIOS chip - Seems like it might be a 
possibility, but don't see why that could cause a freeze when the 
desktop was loaded.

- Clueless here.  What scared me when that happened is that when it flips to my desktop you actually here a "CLICK" and then it loads.  So right there i thought, nice, I probably broke something off the original card.  I had set the card in a plastic ziplock bag, not knowing thats not smart because of the static, wondered if that ruined it.

4. Some other hardware failure on the motherboard - I just don't have a 
clue about which part or function this might be.
I did chat with a tech at HP and his best conclusion was to replace the 
Power Supply and/or motherboard.  That's moot now since I can't get the 
computer to boot into anything, and a new motherboard is not cost 
justified. And the Power Supply tests good when connected to a tester.

- haha, okay this is a little part I left out.  But you have to believe me, I did what I did with extreme caution.  HP Pavilons were not made very well to be upgraded.  In the past I had ordered a GForce 4, way back when, and the card was too long.  It actually would hit some metal petruding off the floppy drive.  There was no way I could install the card without releasing all the drivers and pushing them outward. 

Again, knowing this, when I bought the NX6600, myself and the tech held the two cards up to each other.  The NX6600 was just a bit longer, so small, maybe a cm tops.  As I feared, that made a difference.  It was so close to fitting but I wasn't about to shove it being that I needed to return it if it didn't work.  Protecting the surrounding areas, I brought home a dremel from work, and became my own self proclaimed engineer.  I only had to dremel a small piece of metal, and I did it fast and w/perfection if I do say so myself.  The card then fit nicely.  Its possible small shards of metal might have hit something, but highly unlikely.  I had my hand right down there and nothing was flying off.  Also, when things short out on a board, you'll know.  You'll see bright orange, and then smell that nasty electrical burn smell.

Really grateful for all responses, and glad to hear others have had similar struggles.  Hope to hear more.  No luck yet here but not ready to give up.

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