can you get into BIOS?
maybe the operating system is messed up. some security guard at work had a similar problem on hes laptop. at the end we just formatted it and reinstalled windows.
if you send the mobo back and there is no fault with the mobo, you will be charged a fee (happened to me).
i thought my mobo died, when it failed to boot, power kept dieing after a few seconds. i changed the psu, g card, hdd swapped around the memory modules.
sent it to oc, and they returned it saying its fine. i put the pc back together and decided to use some other spare ram and the mobo booted up fine.
if you can get into BIOS, you can install windows over windows and it will keep your existing files.