New computer fails POST - video problem?

Subject pretty much says it all. I just finished building this thing, I power on, my various fans spin up, the DVD flashes listlessly for a bit, then I get the dreaded beeeeeeep-beep-beep indicating that the BIOS has failed to communicate with the video card.

Here's the spec:
CPU: AMD A64 3000 (mmmm...)
Mobo: MSI K8N Neo4-F, Nforce4 chipset
RAM: 2x512Mb Corsair Value DDR 3200
Video: 256Mb XFX PCI-e Geforce 6600
PSU: 400W

Monitor connects to video card through a old-fasioned-monitor to flat-screen-monitor converter (I don't know the names of either interface).

PSU has a 20 pin output, but the motherboard wants 24 pins so there's a converter on that too.

Help please :(

The D-bracket contains LEDs that will hint you on what's wrong with your shit. Read the code from the LEDs and look in your manual.

Also, a good powersupply is important to a good computer. Sure people have gotten by on shitty PSUs before but if your thrown in PSU ever fails and takes all your hardware with it, all I can say is enjoy the good times.

As for your post code, try googling for "post code *" where * = the bios your board uses. Like Phoenix, AMI, Award, etc.

Another thing, a 24 pin ATX plug isn't necessary to run your computer. Right now I'm using my old Antec True 480w (20 pin) on an Asus A8N-SLI Deluxe, 4x300GB SATA drives, DVD±RW, X800 XL, A64 3000+ (oced from 1.8ghz to 2.53ghz), two 120mm fans, and an 80mm fan.