My pc ain't starting up although it was working perfectly the previous night?

If it's not starting up at all, like you push the power button and nothing happens, make sure it's plugged in, charged, or otherwise getting power. If that doesn't work, take it to the repairman.

If it starts to start but the screen goes blank after the "hourglass" icon disappears, do this:
1) Power off.
2) Power on.
3) When you see it "start to start", hit the F8 key. That might clear the problem.