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however, if your PC is running fine then the power supply is probably fine, the problem comes when you add something in and it can no longer handle it, for example if you put in a new DVD recorder or a scanner that gets all it power from the USB port. Low power supplies cause problems like locking up, the famous "blue screen of death" and computers restarting on their own. If nothing like this happens to you then your power supply is probably ok. If it ain't broke don't fix it!