I had the graphics gtx 460 until it stopped working so i got a 550 ti replacement for the broken one, i tried installing the 550 ti in my computer but the computer didn't recognise the graphics card like it wasn't there at all, the fan was spinning and i definitely had enough power supply to support it, i checked on dxdiag and all it showed up on display was the integrated graphics, i tested it on other computers and the graphics card worked fine and currently i'm using a 9800 gt until i find out why it's not working. i think it may be a motherboard problem since it works on other computers, my motherboard is ASRock N68-GS3 UCC