What is causing this?

I just built a rig for my daughter, specs are below.

On power up, I get a single short beep, fans power up, cdrom flashes, and everything seems normal, but no post. Instead I get many vertical lines on the monitor, (blue in color). If I hit the Delete key, the screen goes blank for a second then comes back with a blue pattern, not the same as the lines the screen is mostly blue with a pattern of lines. I tried holding down the Insert key on power up and got a green pattern, similar to the blue one. I have checked the monitor, it's fine. All components are new except as noted below. I have reseated both Ram and Video card. I have also reset CMOS.
I have tried booting with a Windows 98 CDROM and a boot floppy, with the same results. If any more information is needed, just ask.

Specs:

NF7-s V1.1 (used)
1700 DUT3C (new)
Maxtor 40g HDD (new)
Buffalo pc3200 2*256 (used, just removed from my main rig)
Chaintech GeForce FX 5200(new)
Lite ON CDRW (new)
Floppy (new)
Cooling: SLK-800A W/TT SF2

I would really like to get this going this weekend. She is a GREAT kid and really deserves this.

Have you tried a different video card? If it's display corruption you're seeing, then the video card would be the first thing to look into. You could also try the same video card in a different computer to see if that's the culprit.

i would check the vid card, then the cable for the monitor

I agree w/ johan and bartonboy. When it beeps once when you power up, that means that the system is ok but you just can't see it on the monitor. Check the video card, monitor and all the connections.

I think I have found the problem. I tried the 9500 from my main rig and got the same results. Then I tried an old PCI video card and was able to see the post. I then tried a third agp card and got the messed up video again. Looks like a bad AGP slot.