First thing to try - unplug from the wall and remove cmos battery for a few seconds. Reinstall battery, plug it back up and turn on the comp. Let it start up on it's own the first time to make sure it runs. When/if you see that it does you can restart it and reset all your bios to the way you had them. If it starts again you might have some wrong settings so go back to default or optimized settings and start over with your tweaking. If not then tell us the story of what you got and what you've done to it.