Hi it just gets weirder,
I was writing previous posts from that computer. I have shut it down to try what you have said. Pushed to the power botton to check again, without doing any changes, but computer didn't start. Nothing happened. I have pushed that button for at least 10-12 times, shut power supply's current and opened again, but nothing happened. Mobo's led light is continuously green. 1-2 days ago something like that happened for once, but it started after 2-3 pushs so I didn't think it can be a hardware problem. I thought I could'nt push it rightly.
Power Supply is Thermaltake litepower 700.
I'm brooding on now.
UPDATE: It works again. I don't understand why...