I built my own rig last Novmeber. It was working fine this morning when I went to work. I shut it down went I went to work. When I got home and powered it on. The the case fan and video card fans spin like normal. The heatsink fans sounds like it's spinning at maximum, it spins fast and creates a high pitch tone that's borderline annoying. I'm not sure what could have gone wrong. I check all the connections. The pc will power on and the fans will run at max and just sit there until I turn it off. No beeps from the mobo and nothing comes on my pc monitor. Anyone have any guesses before I take all the wiring out and try to plug everything back in?

Reset the CMOS first off, see if that solves it. What kind of motherboard do you have?

Could be your CPU needs re-seating, It happened to me a while ago.

I have a GIGABYTE GA-P35-DS3R LGA 775 Intel P35 ATX Intel Motherboard. http://www.newegg.com/Product/Prod [...] 6813128050
Thanks for your posts. I think you may be right about the CPU may need reseating. All the connections are tight. I'll reseat the CPU.

I flashed the CMOS and that worked. It booted right up. I find it strange that my pc worked and 8 hours later after being shut off it wouldn't. Thank you very much for the help.

Just as a note of explanation: Most systems are using routines and settings in the BIOS to control CPU and case fan speeds according to measured temperatures. On first starting up, by default ALL of the fans will come on at full speed. As the boot process continues, eventually it gets to where the BIOS can actually read the temperature sensors and start using the control strategy; at this point the fans will slow to their proper speeds. If the boot process never gets this far, the fans will be stuck at full speed.