Hi, this is the first time for me in the forums.
 
My problem is that im getting an error in the system management, the problem is with my graphics cards, I have two EVGA GTX 780 (part number 03G-P4-2782-KR) running in SLI, I bought this cards a couple of months ago, for weeks there was no issues, then I sold my display for an economic emergency, for a month I did not use the computer, I manage to get an spare monitor from my office, when I connect the computer  again it show me an error about windows not loading properly, since I only use this computer for gaming I decided to format the computer.
 
At first the installation went without problems, when I tried to install the drivers for my video cards I lost the Video signal in the monitor, I did restart the computer, again not video signal, I check de LED for the VGA but it was off, then I check for other LEDs in the MOBO, nothing, then I decided to format the HDD again, the installation went without issues, this time I check the system management to see if there was a problem in any part of the hardware, then I see the "Error code 10" in one of the video cards. I tried to install the driver for that video card in particular, windows was unable to install the driver. 
 
I don't know what is going, I tried everything a read on forums, flash the mobo bios to the latest update, reset the MOBO, reset the CMOS, use only two sticks of ram, remove the CPU and put it back again, install all the updates, the services pack, I tried with only one card to see which one was causing the problem, both cards function properly, when I connect the cards separately and check the system management the cards appears without issues, but when I connect the two cards in the mobo the system management shows one of the cards with the problem, then I tried the cards in other system, with a different mobo a P8Z68V-PRO, and the same PSU, both cards showed the same error (code 10), tried the card separately and both card appears without errors, tried both PCI-E ports no issues, tried different SLI bridges and makes no difference, I tried in a third system with the same MOBO different PSU the same error happened, both cards show this error, when the cards are mounted separately there are no issues.
 
I don’t know what else to do, Please HELP!!!
 
I’m sorry for my bad english is not my first language :(
 
My system SPECS:
 
CPU: i7-2600 K
MOBO: Asus sabertooth Z77
OS: Windows 7 ultimate
VGA: 2 EVGA GTX 780 SLI 3GB Vram
RAM: Adata Progaming 2.0 16GB 1600 MHZ
PSU: Cooler master Silent Pro 850W 
CPU: cooler: Corsair H80i
HDD: Seagate 7200RPM 1TB
CASE: NZXT phantom white
BIOS version: SABERTOOTH Z77 BIOS 2104