First off, is this a PC Specialist build? If so, can you please post the full spec from your order page?
What do you mean by 'changing the wires'? Do you mean you tried a different mains lead? If not please try that first. Also try a different wall socket and plug directly into the wall socket, not into an extension lead or surge protector.
What did you do yesterday? Did you move the PC, make any hardware changes, make any software changes, install any Windows updates, etc.?