M18xR2 - gpu problems

Hi, I started to have some problems with the gtx675m SLI, first it started with blackouts, then bsod, and finally showing strange shapes and os not booting up, the error was TDR VIDEO FAILURE, after a few days of drivers, clean windows, all kind of methods, nothing worked, after fresh install of windows, as soon as the nvidia driver gets installed the os restarts, and not booting anymore. The only way was to turn it on in safe mode, disable the second gpu in the list (I think the second in the list was the primary one), and then restart. It was working, now I manage to use the igpu, turned it on via FN +F7, all works fine.
I have seen a post about flashing the vBios, I said I should give it a try, but I have done the big mistake by not downloading the dell one. After flashing all was fine, give a restart, and not starting anymore, it's restarting and then, all comes back to normal, it look like, well, is not..
It's only starting by default on igpu, in bios the dgpu are not shown anymore, is there any chance flashing the stock bios on the cards?
And I think the mistake was the vbios was not uefi, as when the bios is uefi. Now I got the dell stock bios but cannot flash as the cards are not shown..
Anyone who can help?
Many thanks.

 

Both cards are likely dead, as they were based off the 580Ms. Congrats on having them last that long. I recommend getting dual 8950M's (M6100's) for something like $100

 

I don't think are both dead, I was thinking maybe I can recover one of them.
Any idea of how I might be able to?
Is it going to work with optimus, trying to flash it back, one at the time?

 

The cards where on their way out, as shown by you not being able to install the correct drivers or any, and getting that error. You also likely bricked the cards by flashing the wrong VBIOS, and it's not worth the effort to fix