Oh I forgot to give an update. Sorry. ^^; The computer's fine now. Dad believes that the rebooting was caused by the inside of the computer being too cold, since he used the spray on it. After a night of not being used, Jana used it and it was just fine.
So in conclusion: the initial problem of the computer not starting up was caused by dust. Not a virus, not a fried computer component, not a dead monitor, but dust. Just dust.
Well since we now know how to open up this computer, I suspect dad will be cleaning the inside of this computer more often.