PC won't re boot

I've got a PC that's up and running without any problems although when I try to re boot it it refuses to start again unless I turn the power off and on at the back, has anyone any ideas what could be the cause of this.
Thanks,
Fangy.

 

Hello are you sure the pc is not just going into standby or hibernate if this is so just disable both of these in the display properties and see what happens.

 

I don't think it's hibernate or standby, It's doesn't restart when I click turn off computer and click restart or do a reboot when I'm installing something. Any ideas? I've been using the button at the front of the pc to restart it, is doing this bad for the pc?
Thanks,
Fangy.

 

I've checked the power options and it's not hibernate or standby and I've not got Roxio or Direct CD, the computer's got nothing installed bar XP and a few ad/spyware programs. When I got the pc it had ME installed and wouldn't reboot and it's still the same with XP so I don't think it's a software problem more hardware, does anyone know what could be causing this?
Thanks,
Fangy.