I have a Intel Pentium D 915GAV motherboard, pentium 4 2.8GHz processor and 512MB RAM . Computer was working fine . I have bought a new Nvidia Geforce 9400 GT. After inserting the graphics card in the slot, when i turn on, monitor doesnt display anything. But processor fans are rotating at idle speed. So i removed the graphics card and turned on the computer. The computer was working fine. Now i am using the computer without graphics card. Why the computer doesnt display when i insert the graphics card? Is there any motherboard/video card compatibility problems?