Dim 9550 aka XPS? No boot, no CMOS

Hi all, I have a Dell Dim 9550, which I think is also know as an XPS back when it was new. I loaded this up with 8Gb RAM, and four SATA drives with over a TB of storage for video files. Running Win XP SP3, with all updates and patches through the MS EOL for Win XP. I had problems with this machine on more than one occasion.

First doa was a simple CMOS battery change about three years ago. Then a year later I had to replace a WD 320 Gb HD that just up and died, no warning, no hint of troubles. So I put a WD 500 Gb in and reinstalled Win XP and all updates. Probably should have used a Seagate or any other drive than another WD..DUH.

Put Office Pro 2010 and all my video edit, authoring and DVD burning software back on. Ran great for a long time, then got a blank screen, machine was off, and it was left on, with an UPS. So, I dont think there was a power dip or outage, it was set to shutdown if power was lost too long.

So far I replaced the CMOS battery with a new one, no CMOS screen on boot. I pulled and reseated the four memory modules, no luck. Pulled and tried different pairs of memory, and even a single stick. I think it's supposed to boot with one stick, just run real slow.

I am baffled and still can't even get to the CMOS screen. My friend thinks the MB is fried. I hope not. Any help would be appreciated. Take care, Pat C

"Thank God we're not getting all the government we're paying for."---Will Rodgers