no post no beeps no video :(

[Aviator_14]

I have a (fairly) older MSI-6728 Neo2-P 865 PE mobo that refuses to POST no matter what I do. I put the mobo on a cardboard box with the only the CPU, RAM, and video card installed (MB does NOT have onboard video), basically when I short the power switch the CPU fan spins, but the monitor light is yellow and says "no signal." The monitor works fine hooked up to another computer. I have tried three different power supplies (2 of which I know for sure work because they work in other computers) and two different video cards(AGP). I have reseated the CPU and CPU cooler multiple times (CPU installed is a pentium 4 3.2GHZ HT socket 478 and all the pins look straight). I have also tried swapping memory positions as well and there is still no POST, and there are no beeps whatsoever (memory I used was DDR 400 256mb). Also, there doesn't appear to be any sign of bulging/leaking Caps either. I just don't think there is anything else I can do. If you guys can please help that would be great (I want to try to get this working if possible), otherwise I will install the mobo in the dumpster instead of the (really nice) case it was originally installed into, unless someone on here wants it to try and fix

[Ol'Tunzafun]

Before throwing it out, you might try resetting the CMOS by
1) pulling the power from the wall
2) hold down the start button for 5 seconds to drain any residual power from the PSU capacitors
3) pull the CMOS battery for maybe 60 seconds
4) replace the battery, plug it back in, and give it one last try.