Monitor showing now signal

I have just recently purchase a geforce 660ti 2gb. I uninstalled the old graphics shut down put in the new card and saw no signal. So i put the old card back it came on fine. Installed the drivers for the new card. Shut down Put in the new card and once again it said no signal. So i put the old card in and it showed no signal then. New computer. Has a 3.4ghz I-7 processor, 2tb hard drive, 8gb ram, new evga power supply 750watt, almost double required amount for video card. OS is windows 8. The only thing iffy is that the new card is a 3.0x16 and my motherboard has a 2.0x16 but after research found out that that should have no effect. I have the two six pin power connectors plugged into card. The power is running to the card because the built-in fans on the card are running. Any advice? really at a lost her. Has no on board video card from what i can tell.