I've just bought a new HD and mobo for my PC and my PC starts trying to boot as soon as I turn on the power at the power supply. I've trying disconnecting everything from the front panel and all unneccessary parts but it still doesn't work. Also, the CPU fan didn't work until I connected it directly to the power supply.
gigabyte p35c-ds3r mobo
500GB hitachi deskstar HD
2GB corsair xms ram, also tested with 2GB geil ram
I don't get any visual display, so I can't go to bios. It even turns on without being connected to the front panel, and the button on the front was working with the previous motherboard that I had in it.
i am not sure if you got this fixed yet but when i read this:
"Also, the CPU fan didn't work until I connected it directly to the power suppl"
that kind of gives some clues so try a few of these suggestions:
It sounds like the fan wont turn on when plugging into the MOBO but only when connected directly to PSU.
1) Check all your connections again, make sure the 24 pin is in securely and there is nothing damaged on the MOBO side or the 24 pin connector side. Also dont forget to check the CPU and Video power connectors just in case. (it sounds like the PSU and connectors are fine since you had it working with your old board)
2) Pull out the CMOS battery for a minute to reset the bios. Look at all of the jumpers on the board and compare them to the manual to see if they are where they are suppose to be.
3) Since you had an older board it was probably aligned perfect with the mobo standoffs. Now that you have a new board, did you just place it right on top of the old standoffs or did you move them around so it aligns only with the proper holes needed on the new mobo? If you didnt, then the extra standoffs that are touching the board in the wrong place may be shorting it and thus causing the weird power issues you are having.
If all of that doesnt help then you just may have received a bad board. I would put back in your old one just for one last test then if it confirms to work, RMA.