I powered down my computer and removed my old graphics card and then inserted my new geforce 640. I then tried to turn on my computer and nothing came up on the monitors. Strangely, my dvd drive keeps making a noise. So I tried to plug my monitor into the onboard vga slot and no response. I turned off the computer and inserted the old card and did the same and nothing. I have tried every combination and cannot get a display. Please help!