Results of Graphic card malfunction

I just sent my Nvidea GTX480 back to Gigabyte for repair in warranty, but the reason for doing so may be helpful to others when you cannot start Windows 7.................situation, after installing a additional SSD drive, along with a re-install of W7 and FSX, I could not get W7 to display, nor could I get the screen to show up in "safe mode",. after trying various keyboards, mice, etc, I installed a different Nvidea card and the W7 desktop came up.......so maybe everyone knows how a defective card will affect the computer operation, but if not, maybe my experience will be of help.......B42L8