This issue could either be Software or Hardware related. Boot into Safe Mode and check if you can shut down properly.
Refer this link to boot your computer in Safe mode: Start your computer in safe mode
If a problem doesn't reappear when you start in safe mode, you can eliminate the default settings and basic device drivers as possible causes.
Perform a hardware clean boot to determine if any hardware is posing this problem.
1. Go to start and type device manager.
2. Select device manager from the Control Panel list.
3. Right Click on Sound Card, Video Adapter, and Network Adapter one by one and click disable.
4. Reboot the computer. If the problem is fixed then you can enable the hardware devices one by one to find the exact device that caused the problem.
After you found the device that is causing the problem, installing the device’s latest driver should fix it unless it’s a hardware issue.
http://social.technet.microsoft.com/...9-3188e9ffd797
Hopefully you fix
Windows 7 Shut Down Issues.