i had the same problem with my motherobard when i built this computer a month ago, my advie would be to disconnect everything and start again. Add all the major components needed (including that HDD) and also make sure your bios version that came with the board is compatible with everything by going to the board manufacturers site; my problem was i was trying to run a dual core processor and my bios version didnt support it, sent it back to the manufacturer and they upgraded it. Also, check that CMOS jumper, other than that animal's list is spot on for trouble shooting
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