1st build - what's wrong???

This is the first time I've built a computer. I'm helping my 14 y.o. son build his computer.
So far, we have:

processor - E6750 Duo
mobo - ASUS P5K
video - GeForce 8600GT
RAM - Patriot 2 x 1 GB DDR2
LCD - Viewsonic Optiquest Q19WB
DVD - Lite-on 20x SATA w/lightscribe
HD - Seagate Barracuda 7200.10 SATA 320 GB
PSU - Raidmax 12ATX 420W - has 20 amps on the +12

The problem now is that when we power up, the case fans spin, the mobo green light is on, the fan on the graphics card spins, but the monitor shows - 'no connection'. We have attached the monitor to another computer and it works fine. We've tried reseating the RAM and the graphics card. I know the power supply isn't great - it came with the case my son wanted, but it SHOULD be ok. Or not?!! Or, is this a bad graphics card, or is there something else to check? Thanks.

How many +12V rails are there?

You could also try booting with only one stick of RAM in and alternate the sticks as one may be bad and the default voltage may be set lower than what they require.

Note in the OP "PSU - Raidmax 12ATX 420W - has 20 amps on the +12"

This seems awfully small for a 12V rail. I dunno' if he has more than just that one or not...
hope he lets us know soon!

try using that card in another machine. if it works then it's the PSU

Thanks for the advice. I'm not really sure on these PSUs.
My PSU shows:
DC output +3.3 +5 +12 -5 -12 5Vsb
10a/5a 26 32 20 .5 .8 2.0

I can't try the 806GT in another computer - our other ones are all old and don't have PCIe slots.

I did try switching the RAM - tried each one, and in A1 and B1 slots. No difference. It's got to be the power supply in my mind.

The other thing is that this PSU only has a 20 pin + a 4 pin power supply to the mobo (not a straight 24). I've read that you need the 24 to use the dual channels - which means I need a new PSU anyway for the best performance,.(?)

Also - what about these supplemental graphics power supplies. Can I just get one of those to supplement the ATX I have now or am I better off getting a completely new one?

Are you building this PC for gaming? If so what games will you be playing?

Raidmax PSUs are horrible, you should be thanking god your computer is not powering and forcing you to buy a decent PSU, because if it did power , you'll be regretting using that PSU pretty soon. One thing that you should learn about computers is that the single most important part of your PC is the power supply, followed closely by the graphics card, two things you overlooked when you were buying everything. For next time get a decent PSU and make sure the graphics card you get doesn't bottleneck the system so badly like the one you got does.

In fact if you can, take back the Graphics card and buy a decent one on the same price range like the X1950Pro or 7900GS.

Back on the PSU subject, try getting a decent PSU like Corsair 520HX or Antec NeoHE 500/550, any of those 3 PSUs could power any single card setup without a problem.

forget it - after further review - the 8800 gts is the only way to go. we'll get that.

thanks. the ocz 700 gamexstream has 2.