I read the sticky on troubleshooting boot problems, but it didn't really address my particular issue because my PC boots up fine- I just have to turn it on twice. I turn it on and it starts to boot, but there is no beep from the mobo speaker, and neither the monitor nor the keyboard come on. So i turn it off and restart it, and it comes on just fine. It has done this since i built it about 4 months ago. Thanks for any input.
Maybe some part of the PSU is slow to deliver proper output, or is being loaded by system devices starting up. ONE source of this is the hard drives and optical drives. If they all start up at once, it can drag the 12V and / or 5V supply outputs low. Some motherboards have an option in the BIOS to delay HDD start-up for a few seconds, or stagger them if you have more than one drive. See if you can find such an option and set up a delay. That might allow your PSU's output to come up to full spec and stabilize before the motor loads of those drives start to effect them.
What power supply do you actually have? It's probally related to paperdoc's suggestion. I would be concerd you're power dimming your parts regularly which will shorten their life expetency. I've only really seen similar problems and they always pointed at the PSU being a poor grade PSU.
kubes raises a good point. IF the problem is that your PSU's output is being dragged down as it starts up, that may be an indication either that it is too small or that is is a poor-quality unit. In either case that may cause problems for other parts of your system over continued use. As kubes suggested, list here the details of what PSU you have, and the key components of your whole system. Then people can comment on the power supply size you need, compare to what you have, and offer advice on whether to replace the PSU with something else.
Thanks for the replies. But I think that its not the PSU because its a Corsair tx850w powering a EVGA x58 board with an i7 920 stock clock, 6 gb ddr3, and 1 5770. So the 850w should be overkill for that build unless i happened to get a bad unit.