Constant Power Cycle

We had a user’s computer GFX fail on her recently, the capacitor exploded and thus a new computer was assigned to her, after a day working on this new computer .. the computer would not turn on and would go into a constant state of power cycling even after turning the computer off it would turn back on and turn back off. I removed the GFX card and surprisingly the computer worked again as per normal .

There is nothing wrong with the GFX card as it works fine on another computer.

Any Idea’s??