600W is usually sufficient for a regular use build, but with what your running you may be using more power-consuming components.
Well I discovered any keyboard would take up the same power in the USB hub, so I do not think it could be the new keyboard/mouse doing it.
EDIT: I opened up the computer, to discover that my dad had put in a Sound card that wasn't even being used. I took it out, and noticed that it was slightly warm. I turned on the computer and now it works, although, it gave me a "Corrupted BIOS" error similar to one that came up before. It repaired it however. I shall report within a week if there is any more problems.
REPORT: The computer still works. Haven't had a problem, so I will have to award orthokid the best answer.