when I want to turn on my computer I can't just press the power button, I have to either unplug the power supply from the wall and count to like 30, or switch the hard power supply switch to off and count to 30, and the switch it back on again. After that I can power on my system by just pressing the power button. Additionally, if I just turned the system off, I CAN just press the power switch to start it up. But if I keep it off for more than 15 or 20 minutes, I have to switch off or unplug it. Hmmm?

It could be a loose cable from frontpanel to mobo (like just 'hanging' onto the pins, rather than being pushed on them. Or a bad powerswitch on the PC-front.
Borrow someone elses PSU, and see if the problem goes away.
Also sounds like leaking capacitors (i.e. losing their charge, not physically) to me.

try 2 change the system case with a new one maybe this fix your problem

Hi, I am having a similar problem with my daughters EVO D510 SFF Pentium 4.

There is a green light on on the mobo, and for a while when we would push the on button the fans would try to turn, and then stop; then a blinking red light would blink, but nothing else would happen.
Now, nothing happens. The green light on the mobo is still on.

Any advice will be greatly appreciated,
Thanks...

I am new to the forum and am thankful that you are here,
Gary