Here are some more ideas to check too:
1) some motherboards have a hole in the place I circled
in this picture :camera:. So your case would have a position for a standoff there. However, your motherboard doesn't have a hole in that location, so you wouldn't want a
standoff :camera: under that spot. It might cause a short-circuit. If in doubt, remove the motherboard to be certain that the case only has standoffs in places where your motherboard actually has holes.
2) try unplugging all the non-essential stuff, to see if you can get it to POST at all. Leave just the CPU, heatsink, fan, video card and RAM plugged in. Unplug the mouse, keyboard, all drives, all unnecessary cables (USB, firewire, audio, etc) and all extra cards for this test.
3) if necessary, also take the motherboard out of the case and lay it on cardboard, then test it with the bare essentials on cardboard.
4) remove the power cord from the wall, then remove the CMOS battery (the CR2032 battery on the motherboard's surface), clear the CMOS with the CLRTC jumper, reinstall the CMOS battery and plug the power cord into the wall again. Clearing the CMOS sometimes helps fix problems
Once you do get it to POST, if you're installing Windows, be aware that the Serial ATA hard-disk controller has three modes, and two of them (AHCI and RAID modes) require that you supply disk-controller drivers on a floppy diskette (WinXP) or USB stick (Windows Vista) during Windows Setup. The third mode doesn't need drivers during Windows installation, it may be called Compatible mode or IDE mode. This setting is found in the motherboard's BIOS menus.