This message a close parallel to a previous topic: Drive Bay Power Supply w/ Dell mobo?

My E520 came with a 7300 LE video card. The Dell website suggested the EVGA 9500GT 1gb video card as an upgrade. It didn't work - result: PSU fan noise and blank screen.

Figuring that EVGA was serious about the minimum 350 watt PSU, I installed a 600 watt Cooler Master. The install went well. Fan noise dropped dramatically, until I added the the 9500 GT - then I got the same result as before: PSU fan noise and blank screen.

Finally, I called EVGA. The tech rep had me searching for the four-pin power connector on the motherboard. Due to a miscommunication, I plugged a 6 pin PSU connector into an empty socket on the mobo, which turned out to be the connector for an optional media card reader. Power was applied. Now, the "flea power" indicator on the motherboard responds with a yellow light when power is applied.

That yellow light is now the only thing my E520 will do in response to power. It doesn't post. There is no initial whir of the PSU fan - nothing - except the little yellow light. I've gone through the process of removing expansion cards, hard drives, memory, etc. I swapped out the CMOS battery and tried using the original PSU. Still, nothing but the yellow light. Lesson: don't mess with electricity while on the phone.

From what I've read on this site (the aforementioned: Drive Bay Power Supply w/ Dell mobo?), due to the new PSU itself, without me plugging connectors where they shouldn't go, could kill both the mobo and the PSU.

So, here are the questions:

1. Is there any reason to believe that my mobo might not be fried?
2. If I get the mobo repaired, is it true that I need to use the original PSU?
3. Is it possible to replace the mobo with a non-Dell mobo/processor combo (with a view to upgrade speed and memory capacity)?

I am not a gamer. I just wanted the better video card for graphics work, CAD, etc.

Memory (4gb) is DDR2. 32-bit Vista. Desired: 64-bit OS with higher memory limits.

There is every reason to believe your motherboard might be fried.
But to know for sure, you need to remove everything from the board, then do a basic reinstall...
This is to make sure you haven't missed something.]
I would test with the old setup, original hard drive, original power supply.. and keep all the new stuff off it for now.

This same sort of thing happened to me, i just took out everything i wanted and put them in a different computer.

update

I checked the new PSU with a multimeter. I got all three voltages. So perhaps it's only the mobo that got fried.

Comparing the pin configuration of tthe original Dell proprietary 20-pin PSU connector with the standard one on the new PSU, I can't imagine the mobo being anything other than fried. There was every combination of power going to ground and mismatch of voltages.

I will do a reinstall to check, as suggested. If the mobo is toast, keeping desired hardware, like the man said, I'll either do my first re(build) with a standard ATX mobo, I7 with 12 mb of ddr3 memory, or buy the same prebuilt.

This is my first serious venture into computer guts. I learned plenty.

Thanks, guys!