SOLVED Problem SLI'ing GTX 670

Hey guys,

I'm trying to get 2x GTX 670 SLI to work on my recently built rig.
The problem is that when I have both cards installed, I go to the nVIDIA control panel, and turn on SLI, it would do the usual screen flash a couple times then it becomes black screen instead of showing up the desktop. I can press CTRL+ALT+DEL and the screen will show the usual splash menu to lock computer, log off, start task manager, etc and I can shut down/restart the computer from there. I tried clicking on task manager and it would go back to the black screened desktop where I can't see my mouse pointer either until I hit CTRL+ALT+DEL again to bring up the splash menu. I have tried using both cards individually, and also individually tested out both PCI-E slots and both events have proven that they aren't malfunctioning and that the problem does not come up individually. I have as well reinstalled the video drivers and the problem persists with the 2 cards installed.. I can't imagine the PSU being the cause as the components together barely goes over 500W. >_<

Any help is appreciated.

SPECS:
Windows 7 Ultimate 64bit
Coolermaster Storm Enforcer Mid-Tower Case
Intel i5-3570K
Gigabyte GA-Z77X-UD3H Mobo
Kingston HyperX 8GB DDR3 RAM
Adata SX900 128GB SSD
2x PNY GeForce GTX 670
XFX 650W PSU

flip the SLI bridge

UPDATE..

I was able to troubleshoot and fixed the problem I was having.

Apparently Windows was trying to install it's own drivers to run the cards and was conflicting with nvidia's drivers. I ran the system through safe mode and uninstalled each card's drivers and did a complete wipe of old drivers using driver sweeper. Restarted the computer and booted up to Windows, let Windows finish it's plug'n'play gibberish then went on ahead to install nvidia's drivers, restarting at each step of the way.