Sager 2090 Colorful Vertical Lines (GPU?)

Hi,
I've owned a Sager 2090 for about 3 years and have encountered a problem which I first thought to be a GPU failure. When I booted, multicolored vertical lines would appear over the entire screen (like a bar code), starting at first vague, and then getting progressively darker and more defined. Disk seemed to be spinning normally. Figuring that only the display was not working, I tried waiting and entering my password to see if I could enter Windows (and hear the corresponding computer noises that process makes) but I do not think the computer was in a state to receive my password and boot fully. No start up chimes were heard.

The result looks exactly like what happened to this poor guy on YouTube:
YouTube - ‪Nvidia Video Card Failure Dell XPS M1330 GPU‬‏
Hope links are allowed. Sorry if they are not.

Anyway, plugged in a monitor to the VGA port and didn't get anything.

Ordered a replacement GPU, installed it, and now the machine boots up for a few seconds and shuts back down again and then repeatedly continues to try to boot up in a similar fashion without me pressing the power button. Screen remains blank; no colorful vertical lines can be seen.

A computer savvy friend who helped me with the new GPU installation thinks it could be one of four things:

New GPU is broken, Motherboard is broken
New GPU is broken, Motherboard is fine
New GPU is fine, Motherboard is broken
New GPU is fine, incompatible with Motherboard

I've had overheating related shutdowns for the last two years it seems and I've heard the GPU is prone to this. (Rigged up an under-table fan that keeps my laptop cool, and prevents overheating, but without this quick fix, it overheats quite easily).

I've already invested $125 in a new GPU. Would any more investment in replacement parts (like a motherboard) be too risky?

If you fine folks have any experience with a similar problem and know how I should go about with a fix, I would be very, very grateful.

Thank you in advance.

 

Just shooting from the hip, did you check all the connections, make sure everything is connected again properly?

Here's a disassembly guide (props to theriko) for that model if it helps:
IFL90_ch5-Disassembly Guide-intel.pdf

 

Yeah, my friend who installed it for me is a professional computer tech and he made sure everything was in place. I'm pretty sure we used that very same disassembly guide as well.

I mean, of course the possibility exists that something didn't get reconnected correctly, but if that possibility was zero, what other problems could there be?

Also, thanks for taking the time on this. I ordered the computer from Xotic, so I appreciate the attention you're giving me.

 

I tried some searches and this symptom happens with a dying or improperly seated (crooked) GPU. You replaced the GPU so maybe it's hopeless

 

Only other thing I can think of is a BIOS update...but if it is the exact same card that shouldn't be necessary. Any luck so far?