I need to know what I need to do to get a radeon 9200 agp video card working in my dell gx270 it has onboard ,

dell gx270 has onboard video and its set to auto in the bios but when I install the new card and start the computer the screen says no signal even when I try both the onboard plug and the plug on the new card. Please I need some instructions on how to resolve this problem. The radeon 9200 is a 128 mb card.