Go to the Gigabyte support and make sure your processor is supported, AND that your current BIOS supports the CPU and does not need to be updated. I assume all memory sticks and your CPU are fully seated. Power supply connection into video card and CPU additional power. I take it there are no beeps. Be sure to have disconnected all drives including power cables, and any
other expansion and front panel connections connected to the motherboard headers, as well as unplug any external connections (USB, eSATA, etc.) that could be a source of
problem -- just to rule them out.
1. If you have tweaked your BIOS, go back in and reset it to to its safe default (or reset the CMOS if you cannot get into BIOS menu IF you have made adjustments to your BIOS). See if it boots.
2. Pull all your memory sticks. Stick one back in and make sure it is well seated. [I know you seem to be doing this, but I want to be clear.] See if it boots.
3. Replace the stick with another stick in a different slot (preferably a different channel). See if it boots.
4. If you have any slower DDR2, especially 800Mhz, try a stick and see if it boots.
5. Pull video card, and see if it "boots." Report results including beeps.
6. Replace video card. If you have a compatible Pentium or other CPU swap. See if it boots. [If it does and it is stable upgrade to newest non-beta BIOS. See if your new CPU will now work.]
7. If it does not boot, I would say odds are its the motherboard at this point ... though it is possible a faulty power supply could still be giving you boot problems. If you have a spare of sufficient power, you could try swapping power supplies.
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