Mostly copy pasting this from a post I made on /r/techsupport. A lot of people here seem to be good on providing support so I hope y'all don't mind if I ask for some assistance!
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Hey guys, I recently went over to a friends place to help him swap out his old GTX 650 with a GTX 660. Everything turns on normally, installed the new drivers and everything went smoothly. When we booted up MGS: Ground Zeroes to test it out, the pc just completely shut itself off after passing the logos. There is a blinking blue light in the front of the computer, and the pc won't turn on until we unplug and plug the power back in. I've also noticed that there's a single beep that plays out every time we turn on the computer. I tried removed the GPU and wiping off any dust that might be on the connectors but I'm fairly certain that it's a power supply related problem.
The specs are:

RAM: 8GB DDR3 SDRAM

Storage Controller: SATA II

Hard Drive: 1TB - SATA III - 7200 rpm

Optical Storage: 24X DVD±RW Dual-Layer Super-Multi Drive

Graphics Controller: NVIDIA GeForce GTX660

Digital Video Standard: HDMI / DVI / VGA

Power Supply: Turbolink Switching Power Supply Model ATX-XG500W 500 Watt - AC 120/230 V ( 50/60 Hz)

Audio Output: Integrated - High Definition 5.1 Channel Audio

Operating System Provided: Genuine Microsoft Windows® 7 Home Premium 64-Bit Edition

Extra things to note: We ran games that were not as graphics intensive such as League of Legends and Transistor and they work fine, it only crashes when running games that would need more power to run. There is also a small flip switch on the back of the power supply unit, it's currently on "120V" and can be flipped to "230V" but the monitor just remains a black screen if we try to run the computer on 230V.
Hope we can get some help, thanks!