PC won't turn on

I was playing an online game, and then a few minutes later I got a screen froze. I restarted my computer, and the PC was working, but after 10 minutes I got the screen froze again, so I just restarted it again. The same thing happened 2-3 times, then, the last time I turned it on the PC was black, it won't turn on at all. I don't think the cause is the PC, because I tried to connect my computer with another PC that is working just fine, and the PC didn't turn on. I checked the CPU, it wasn't the problem, I don't think it's the motherboard either.. My computer is Windows XP , 32-bit.. Can anyone help me?