Laptop won't boot after bad overclock attempt

I have an ASUS G750JX laptop ruing Windows 8.1 that's recently been experiencing difficulty booting. The hard disk light flickers off after a few seconds and the computer just sits on a black screen until it's tued off.

Previously, holding the F2 button would cause the hard disk light to flicker weakly for a while, and the next attempt at tuing it on would be successful, but now that won't even work. The hard disk light is on, and shutting down requires holding the button down longer, but the screen stays black.

A bad overclock attempt which caused a crash alongside severe graphical glitching occurred immediately before the problem started.