So, terrible, terrible power supply. Please read this, use translate on Google Chrome if you have language barrier problems. That power supply should be replaced with something that has actual quality, to begin with.
Below you will find MY standard list of recommended power supplies and beyond that this thread is intended as a landing place for questions or discussions regarding specific units, platforms or related PSU tech, all of which are all welcome to be discussed here. If it's related to power supplies...
But, also, that graphics card is like 12 years old, so the fact that it has problems should come to no surprise to anybody and it is extremely common with faulty graphics cards, or power supplies, for it to work "ok" with no full featured drivers installed that will utilize full power draw, but to not work at all once full driver support is in play.