I will tell you the story behind the problem. The computer needed to be reinstalled, it has 2 HDDs so I had to un-plug one to see which is which, to save as much data as possible. After unplugging the first one, it booted with the reinstallation CD, it wasn't the HDD I was looking for so I turned it off and unplugged the other one. After unplugging and turning on, right after booting test, the HDD was turned off, only the CPU fan was working. Turned it off with the power supply's button help, holding the power button didn't do it. And now it doesn't want to turn on anymore. I tried with another test power supply but the result is the same, doesn't want to turn on. Any idea?