Bonehead mistake costs me about 2 hours

[CORed]

I added memory to my Windows box (Dell desktop) today. boosting it from 512Meg to 1.5Gig. One of the simplest things you can do inside a PC case, and something I've done many times before. No problem, right? Well, I get the memory installed, plug everything in again, power up. No video. Machine appears to be booting, no beeps, but video is dead. I fiddle with it for about two hours, try old memory only, new memory only, check that all power cables are connected, check HD data cable, check that video card is seated. Finally, I notice that I have repeatedly plugged the monitor into the disabled onboard video controller instead of the video card. Doh!