It's been a while since I've had a desktop PC but I distinctly remember that my old desktop's power supply had a manual toggle that you flipped depending on the input voltage. This was pretty standard from my experience. In any case, most modern power adapter bricks are dual voltage input. At most, you can likely swap out the power supply on the desktop and go on with your life. It's easy enough and not too expensive from the many computer parts retailers online (assuming your desktop is a standard form factor one)