My computer has been having problems lately in the area of it not turning on when I want it to. When I turn off the computer by the shut down button in Windows 7 it will shut down properly, but when I come back to turn it on it doesn't want to. I tried to troubleshoot a little bit and found out that if a unplug the 24-pin motherboard connector and press the power button it will sometimes turn on, other times it won't turn on after unplugging it. If it doesn't turn on after unplugging it if I leave and come back a couple of hours later and try again when I unplug the 24-pin power and press the start button everything acts like I want it to.
My computer is about 5-6 years old now so it's getting on the older side, but here's where the question comes in. What is causing this!? I have a suspicion that it's either the power supply or the motherboard. I am planning on getting a new computer by christmas and I have extra money now so if it's the power supply I can replace it now, but if it's the motherboard I need to wait until christmas. So what do you think is causing this problem?
I had odd power on problems that seemed to go better when I pulled out the power plug. Ends up it was the RAM. I had two of three ram sticks bad. Try pulling one at a time out and see if that helps. RAM can give you really odd problems.
You might want to try removing components/accessories one by one and see if you can narrow down anything that might be conflicting. I've seen issues with PCs not powering on or off from things like power connectors connected to auxiliary inputs on PCI firewire cards, or powered USB hubs connected to USB ports that have the +5VSB running through them for USB keyboards with power on buttons, etc.
I'd try removing any extra USB devices first and see if they're interfering.