Okay so I decided to build my own PC. All the hardware is compatible and works fine except for the graphics card. When the PC boots up the fan to the graphics card turns on but when I go into devices the computer doesn't even recognize it. I am currently using the onboard graphics card. The first graphics card I used was a Radeon HD 5570. I switched out monitors and neither worked. I thought it might have been the graphics card so I returned it and bought a better GTX460. I installed it into the PC and when I boot it up the same thing happens. The fan on the graphics card starts running but the motherboard doesn't seem to recognize it. I tried reseating the graphics/memory cards. I updated the BIOS for my motherboard and that only caused a headache for about an hour. I'm really lost on what to do right now.
Mobo: Asus M4A78T-E
CPU: AMD Athlon II Quad core 3.0ghz
700 watt corsair psu
When you installed the new card, did you go into the BIOS and disable the on board graphics? I know this might sound a bit stupid but did you plug the monitor cable into the new graphics card? If so, try both video ports on the on the card.