Right, here is the story.
I have a Nvidia GTS250 that I thought was about to die because it started to freeze, with repeating sound, and the fan would have hiccups.
Then it wouldn't even show anything anymore. I tried it on another computer and it's working fine no hiccups or anything. I then started to suspect either the PSU (which was builtin the case and is 500W 12V1 @ 18A and 12V2 @ 16A) or the motherboard(even maybe the PCI-E slot, I've only got one...).
I tried another graphics card less energy-hungry and still no video (my mobo doesn't have onboard graphics) So I'm not sure if it's my PSU (I tested the electricity and it's all good, every rail has the normal load) or my motherboard. Any suggestions ?