Five minutes to Post Bleep

My PC is Win7, i5-2500K, 16GB RAM, 980GTX, ASUS P8P67 Pro Rev3, various HDs including SSD for OS, with 3 monitors in surround mode.

Over the weekend my PC crashed with a buzz through the speakers and then dead screens, the screen that normally shows the POST messages as it boots was still recieving something therefore no message about 'no input' came up like the other screens.

After about 5 minutes of sitting there dead to the world, there is a beep and the PC comes back to life as if nothing has hapened, and continues to boot up fine and runs like normal.

This morning I booted the machine up before work and it again took about 5 minutes to POST again.

Any ideas what to look for before I have to start buying bits and swapping out parts?

I would investigate the BIOS. 5 mins means it could be mem testing the whole 16gb! See if it can save your settings which would indicate the battery is fine.

Can you restart OK? Is shutdown and then power switch working OK?

Not really sure what's wrong tbh.

Thanks for the suggestion, I tried changing a setting in the BIOS last night and then rebooted to see if it was remembered and it was.

Next thing I tried was to unplug all the additional USB devices, joypad, joystick and throttle to see if it made a difference, nope.

On reading through the manual the ASUS board has POST LEDs to indicate what part of the boot it is doing and so that you can see where it has stalled. So I took the side of the case off and booted again, it flashes through the CPU, DRAM and VGA LEDs and then spends around 3mins with the BOOT_DEVICE_LED on, and then just boots as normal.

More investigation I think.