Windows 7 has a live preview thumbnail of your running programs when you hover over the icon on your taskbar. Some people love it, like I do, and others don’t care for it so much. Here is how to disable the thumbnails on your taskbar.
1. Open regedit (Start > type regedit and press enter).
2. Naviate to HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionPoliciesExplorer
3. In the right pane, right click and select “New” and “DWORD (32-Bit)”. Give it the name TaskbarNoThumbnail.
4. Right click the new name and select “Modify”. Change the value to “1“.
5. Close regedit, reboot (or log off and back on). You will no longer have the taskbar thumbnails. To reverse it and get your thumbnails back, just delete the new key you created or change the value to “0“.