ASSUMING HERE.....I take it your system didn't have a video card before and you used the int. video port. If so, you need to disable the video port to allow access to the new video card. I would check with Dell or review the help guide provided with the video to see what it states. You need to enter the bios(if applicable) and disable the on-board video port. Then when you reboot hopefully, it'll start the process to access and/or load any drivers needed for the new video card.
I just recently bought a XFX Graphic's Card GeForce 8600GT Profess1onal Series and tried to install the hardware into my computer. When I turned my computer on , it say's I have to plug the monitor cable into the Graphic's Card connecter. I did as I was told and when I restarted the computer. The monitor is on Power Save Mode and I cant see anything. The power button on the monitor is amber lighted and I can log into a window's user name by using the keyboard alone and I hear it working. My friend's said it was my power supply so I bought a PSU Raidmax 630W Power Supply. It still didn't help. My computer info is..
Operating System - Microsoft Windows XP Home Edition(5.1 , Build 2600)
System Manufacturer - Dell Inc.
System Model - Dimension 4700
BIOS - Pheonix ROM BIOS PLUS Version 1.10 A03
Processor - Intel(R) Pentium(R) 4 CPU 2.80GHz (2 CPU's)
Direct X - Version 9
Memory - 502MB RAM
Please help me. Any advice or help is appreciated.