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#11
Hi Tsram
Through all given advice above and what you had tried by combining power from other source (laptop) with your Y cable, it's pretty obvious that you have under voltage problem. It could be coming directly from the PSU, or voltage regulator on the MB, or, most of the capacitor handling USB voltage supply started to get dried. Trying to directly supply/combine the 5 volt on your USB cable from the PSU is not advisable as it may interfere the MB voltage regulator. the USB voltage is delicately regulated. It is used to manage the USB device when connected/disconnected. Its true if you see some USB HDD come with 5 volt external adapter but it's mainly to help spinning up the disk plate and it's isolated from the USB port.
In normal way, you will have to try replacing the PSU with new one (or borrow one if just for testing). If it doesn't work then you may conclude that the MB is almost out of service though it works for the mean time.
But one thing. You haven't mention it was rear or front USB panel. If it was front, then try with the rear panel.
Hope that help you some.