Anishkalsi :
hang-the-9 :
Yes that is a low quality power supply, but your CPU is also too slow to play GTA V on, unless you are OK with poor results. E8400 is not a bad CPU in the Core 2 Duo range, but it's bellow the minimum that GTA V wants. If you run the game at 720 resolution, you may be OK get playable frame rates with some lag and stutter in areas. If you want to play GTA V at 60 frames even on lower settings, you need to get a new CPU, and maybe a new video card.
Yea I know my cpu is old but I've also tried with euro truck simulator 2 and I've used game debate to check my specs and it says I can play it on high settings but I cant
Your CPU meets the minimum requirements, that is not enough to play on high settings.
These are "recommended" requirements which is what you need to be to get to medium and higher settings.
Euro Truck Simulator 2 Recommended Requirements
CPU: Quad core CPU 3.0 GHz
CPU Speed: 3.0 GHz
RAM: 6 GB
OS: Windows 7 64-bit
Video Card: GeForce GTX 760-class (2 GB)
You will just be going in circles with trying to play newer games unless you upgrade the CPU and video card to one that does not crash at full speed. That includes the power supply if you want to minimize the chances your power supply does not fry the rest of the components at some point.