One Computer Is Malfunctioning

I'm using only my Windows and Mac computers because my Ubuntu Linux box has some kind of problem: when I turn on the power supply switch, the fans spin up, then spin down, then spin up, etc. The monitor displays nothing. I don't know what's broken.

It's my best and most-used computer. If I haul it along to the signage party on Friday, would there be time for anyone to take a look at it?