Motherboards Gigabyte GA-H61N-USB3 wont power down

Hi, I've just upgraded my dad's PC from XP to a fresh install of windows 7. However when I power down I get a black screen but the systems fans HDD ect stay on and sometimes though not always after a while it will reboot. I've checked my cabling and it seems fine iv updated the both windows and the motherboard BIOS and I just can't work out what the problem is. Any advice would be rely appreciated
Many Thanks
Ben

 

just a little update iv installing windows 8 onto another hard drive and I get them same problem

 

It's probably a bios setting mate.

 

Thanks ill have another look and see if im missed somthing