I recently got ASUS H67 mobo and today I smelled burning capacitor when I turned on the PC. I also saw a bit of smoke rising from the board/CPU not sure it was that area. I got no display/POST/beeps of any sort. Checked the case and CPU fan was not spinning while the case fan works okay. Took out the RAM and no beeps at all while green light is ON in motherboard and a red one for some mem okay. I disconnected everything and still no power to CPU/no post/no beep. Furthermore, When I turn the PC off, I see the GPU (6870) fans spin for a second (when the GPU was in the PC).
I am not sure if this is the PSU or Mobo, The mobo is fairly new so I can return it tomorrow if thats the problem and get a P67 I am not sure if its the PSU since it seems to be lighting up the case fan but going to get my multimeter out soon.
Oh one more thing, I can hear the hard drive spinning :S
Smoke is not a good sign. It's remotely possible that it was a residue left on something that got hot (because the board is new), but it doesn't sound like it.
Yes, it could be the PSU, and if you had a spare handy, it wouldn't hurt to try it, but my guess would be that it's the motherboard.
I just saw a comment on someone else's problem - you did check that both power cables were plugged into the motherboard? That is, the large 20/24 pin cable and the smaller 4 or 8 pin cable? Leaving out the second cable is not uncommon, and it could produce results like this.