I also started looking for solutions on google, but it was difficult too and not there accordingly. Finally ask aja deh to my friends who understand the computer. So now I will share how to fix Windows Desktop Manager in Windows 7.
Fix Error Desktop Window Manager Stopped Working
1. Desktop windows manager does not work like the picture below.
2. Click "START"> "Control Panel". After selecting "Control Panel", choose "Services" in the "search" field. Like the picture below. Then will appear "Administrative Tools", select "View local services". Like the picture above.
3. After the click will appear a new window and search "Desktop Windows Manager Session Manager" then click2x or select and click "Restart" like the picture below.
4. When in klik2x it will pop a new window then click "Stop" then click again "Start". Then select "Apply" then "OK". Like the picture below.
5. Done, You can see the result as the picture below the taskbar color has changed.