Broken......

I have a Gigabyte 8ihxp motherboard and a nvidia 4600 video card... When I turn on the computer the light on the monitor goes yellow... The monitor works, And when I tried it with a mx400 I got the same thing... Any ideas?

So what exactly is happening here? Your computer doesn't boot up? Or your monitor just isn't working properly and not showing what it should? How many beeps does it give when you boot up?

Hmmm, I tried a PCI and AGP video cards...... Neither work, The monitor works on another computer..... The computer wont boot up

Are there any error beep signals when you boot up?
eg. 3 beeps in a row?

Well.... check the power connection to motherboard and place the RAM correctly (might be some loose connection). I think this will do.

I had the same issue where in the video display boards I was testing were just not compatible with the Mobo I was using.

Recommendation : Try a slightly older display board if you have one floating around. I would imagine the machine will boot and the display will work as normal. Symptoms indicate hardware incompatability.

Reason for recommendation :
The hardware configuration inside the case I built : Supermicro S2DGE mobo supporting Dual Xeon 450's, 512M PC 133 ECC Registered non buffered ram, AGP slot supporting 2x and 4x. Video Card attempted to install : nvidia geforce 3, 64M DDR
Results of that configuration : system would not boot and the monitor pwr indicator turned orange/yellow (my lame as monitor putting itself to sleep for lack of signal??)
So I say WTF and take the following steps :
Moved the video card to a different machine to ensure it worked at all with the monitor in question. It did. When installed in a slightly newer Mobo with a slightly more powerful chip, it worked like a champ. Installed a slightly older card, ATI All-In-Wonder Radeon 32M in the dual xeon box, and boom it boots fine and I have video through the same monitor. So I'm thinking alright, lets try another slightly newer card to see what's up. So I bought a 1 ATI Radeon 7000 32M, agp and an ATI Radeon 7500 32M DDR, agp. I tried each of these in the xeon box. Found that the mobo absolutely would not support a video card running DDR memory for some reason. I could up the clock speed on the chip till I was blue in the face and it would be okay, but running a video display board with DDR memory and it would not boot. Same symptoms you have described.

Now, I know that the mobo you have is new and the video board is new, but the incompatibility may still be there. Just a thought.

Hope this helps you out at least a little.
Regards and good luck.

edit : I had also attempted to use an nvidia chipset with ddr memory on a pci based card. Same effects as the agp based card with ddr.

I know this is going to sound really stupid, but I had the exact same problem with a system I was building for a client. It was a brand new motherboard and, as you said with your problem, neither a PCI nor AGP video card would work properly. It turned out that the connectors were simply extremely tight and I had to bear down on the card harder when I tried to insert it. Once I figured that out, I installed the AGP card and it worked without a hitch from that point forth... might want to check that... it may not be getting a good connection.

AJ

I have to agree with avdven. I had the same problem myself once, and have a good friend who also has experienced the same issue. Both of us resolved in the same manner and since I have always followed that procedure, which is to make sure the AGP card is WELL SEATED. I sincerely hope that this gets you going too.