I have a homebuilt system that has been giving me headaches on and off for the better part of a year. Whenever I try to shutdown, sleep or reboot (from Windows or BIOS), the system will appear to shutdown, but will not power off (fans and lights stay on). The only way to power it off is to hold down the power button for a few seconds. If I immediately try to turn the system back on, it will fail to POST. However, if I leave the system alone for an hour or so after powering it off, or unplug it or about 10 minutes, it'll start back up and boot to Windows without issue.
I have tried removing every component and powering it back on, save for the CPU, mobo or RAM, and nothing changes. I would replace a faulty component, but I don't know what to replace. The dependency on letting the system sit after power off makes me wonder if the issue is power related (either PSU or mobo). Interestingly, if I boot to linux on a separate hard disk, it will power down fine. This makes me wonder if the issue is related to the SSD Windows is installed on (the boot loader is on the SSD too, though).
I have updated every driver and BIOS multiple times. As of this post, all of the drivers, and the BIOS, available from ASRock are up to date. I also upgraded the SSD firmware successfully, but with some difficulty (due to the issue rebooting). I have looked at the Windows event viewer, and there are no errors or warnings when the command to power down is submitted. Windows seems to shut down correctly.
Given these symptoms, what would the likely culprit for these problems be? Would it most likely be a hardware problem (SSD, Mobo, PSU), or software problem (Windows, BIOS)? All of the remaining avenues for tackling this problem would involve spending money and/or data loss, which I would like to avoid if possible.
Here is the setup:
Asrock Z77E-ITX Mobo
Intel Core i5 3570K
Crucial M4 256 GB SSD (Primary drive) with Windows 7 64 bit
Segate 1TB HDD (Secondary) with Ubuntu 12.04
WD Caviar Green 2TB Drive (not in use)
Corsair 1600 low-profile DDR3 RAM, 2x4GB
EVGA GTX 660 ti
Antec Khuler 620 CPU cooler
FSP SF 450w PSU LG BDR Drive
Update I bought a new power supply and shutting down/sleeping/rebooting from Windows, Linux and BIOS. Unfortunately, after a hopeful 5 minutes, the old problems started resurfacing. The first time I shutdown from BIOS, it failed to POST. After that, when the system would POST, Windows failed to load half the time. This is actually a step backwards from the previous state (Windows never failed to load if the system POSTed).