Computer turns on and off when connecting graphics card

Jorge90

Honorable
Jun 7, 2013
8
0
10,510
I opened my computer to clean it up a little bit.
I've done this lots of times but this one is causing me some problems.
When I connect my graphics card (nVidia GT240) and I turn on the computer, after a few seconds everything turns off (it's easy for me to see it because I have Fans with LEDs) and then turns on again automatically.
The problem is that when I connect my HDMI cable, the screen does not work, so that led me into thinking it's a graphics card problem
How can I check if I'm correct or not?

PS: It's not a problem of the PSU, it has 500W