I don't know how to explain this in words clearly, but my Windows 7 computer used to be able to show only a particular window if I hovered my mouse on the Taskbar. However, I don't know if I set anything but I install and uninstalled a program and it's no longer giving me this.
Notice in this image a cursor is hovered on the bottom of the screen and you see a mini-sized version of the window?
You can either right click the desktop and Personalize, then choose an Aero theme, or there is an Aero troubleshooting tool under Control Panel\All Control Panel Items\Troubleshooting -> "Display Aero desktop effects" (can be slow to load)
I found that if you run the Troubleshooter, which panhandel recommended, Windows should tell you what your problem is. Once you know you should be able to attempt to resolve your issue. For me however, I run VNC on our machines. In the bottom right corner where the icons sit, I right-clicked VNC > Stop Listening (or stop service). Aero worked immediately after closing out VNC Viewer (user mode).
Lastly, if that doesn't fix the problem, make sure that your display settings for Windows is set to Aero Theme.
Go to personalize and select an Aero theme.
Right click on taskbar > properties > make sure use aero peek preview is checked.
Try this. Go to Control Panel > Device Manager. Under "View" select "Devices by Type" and see if you have a 64 bit driver. If you do, disable it and re-boot. I had the exact same problem. This fixed it.
Mine has a 'DameWare Development Mirror Driver 64-Bit' listed. I disabled it and re-booted.
Go to Regedit and add/modify the registry key shown in the image below, then reboot your computer.
