I have a problem with a computer that wont reboot from windows xp. It wont completely shut off to "restart". I have to PUSH in the power button to turn it off so I can turn it back on. The computer will however "shutdown" when selected to do so in xp. Any ideas?When did this problem start?

Windows Shuts down, but doesn't restart?
Have you added any hardware just prior to this problem ? If so , take it
out and see what happens. One other THING , try restarting by the
keyboard : Windows Key+R+Enter . Xp  still has a lot of unsolved problems!the computer works fine otherwise. I can BOOT it up and run it, it just wont "restart". Honestly, it all started after I tried windows beta 7 for a few days. I noticed it then and thought it was an issue with the OS because its still in the beta stage. When I reverted to XP with a complete format, the problem  carried over. ok, alittle story here. So i went into the bios to take alook at the power management options. I set everything to default in case something changed. I saved and exited and then nothing. The power flickered a few times and then just the power light and HD light came on. I thought "great, I fried my motherboard overclocking". but then i thought, there is no way. Everything was working fine, this has to be a PS issue. So I turned the PS off and on a few times and still nothing. As i pouted for a few hours contemplating a RMA, I decided to unplug the PS and try it again. Poof.... it worked and now it reboots fine from Windows . OK so what was at play here? Is the PS going bad or could it be the motherboard? I also un-overclocked it and figured after that scare I'll just go UPGRADE my processor. 
I decided to unplug the PS and try it again. Poof.... it worked and now it reboots fine from Windows . OK so what was at play here?

Age old trick....unplug the mobo..it's denied  juice..the caps are
drained..it resets itself and voila!..it works. Keep your fingers
crossed..knock on wood!