good evening,
first of all, i'm am a newbie when it comes to this video card stuff, but i'll share what worked for me.
I recently purchased a AGP ATI Radeon X700 Pro (256 ram) for my Dell 4600 series computer. I followed the directions to the letter. I unistalled my drivers for my integrated video card, powered it off, installed the Radeon, plugged in my moniter into my Radeon, turned it on and WHAM. nothing..... so i unplugged the the monitor, plugged it in the original connection and turned on the computer in safe mode. I system restored my computer to an earlier time. now, back to square one. I repeated this ENTIRE process around 2 or 3 times before i figured out that somethings wrong. well, several hours later and surfing the net for help and solutions. I read something that helped. the article said that he had a similar problem but the culprit was his PCI slots. So, i said "what the heck". I went to my device manager - other devices - PCI simple comm contr and DISABLED it.
I then went back and did the entire process (unistall drivers etc... ), said a little prayer and turned the computer on and WHAM!!! IT WORKED. Windows came up with "found new ...". I Cancelled all of those and installed my drivers. So, after 7 long hours of feeling hopeless and confused, it worked. I hope this helps!