On the back of the PC near the power cable, there is a small red switch, please make sure that switch is set to 115v.
After this has been verified, unplug the power cord from the PC, but leave the power switch set to on.
Hold the power button on the top of the PC case for about 20 seconds.
What this will do is drain the Power supply completely of power.
Once this has been completed, go ahead and replug the power cable, reboot the PC, and see if the problem persists.