Biscuit

So after 3 years of my HP Slimline working without fail, something finally went wrong. I replaced the cooling unit roughly 5 months ago from a standard fan to a liquid cooled unit. It's been working like a charm for the past 5 months but two days ago the system began making a revving noise from the power cell. Other than that, the computer sounded like it was starting up fine... I say "sounded" because no video was coming up on the monitor. So I couldn't tell if it was actually booting up. I replaced the powercell and got the exact same result. Revving noise from the powercell and no display. Any idea what the issue could be? Did the motherboard go? Thanks, Biscuit