Computer will not power off?

I have had my computer for 6 months and have had no issues. However this weekend I rebuilt it in a new case (corsair 300r) every thing works good turning on but turning off is a different story. When I go to turn it off windows shut down but the tower doesn't the monitor turns off with windows but the tower stays on. Can someone help me solve this problem thanks. 

I remember having this issue some years ago. I found out that it was something in the os that caused the issue. A reformat fixed it for me.