Computer Keeps Crashing for No Known Reason

[McRona1d]

Hello, my pc is crashing repeatedly at no obvious reason. I have no clue where to start and I would really appreciate if someone could help me. All I know is my fans change from white to rainbow and most stuff that I had up works, but I can't open anything else or even shut my pc down or restart it. I have to use the reset button on the front and I don't like doing that, but it is the only way I can get it working again. Also I don't know if it was a glitch, but my gpu says it is at 100% usage on the task manager.