If you receive a message that some visual elements, such as window frame transparency, have been turned off, or if you receive a message that the theme has been changed to the Basic theme, one of the following might have happened:
A program that you're running is incompatible with Aero themes. When this happens, some visual elements are automatically turned off. When the program is no longer running, the visual elements that were turned off are turned on again automatically.
Your laptop might be running low on battery power.
Windows might turn off Aero themes or window transparency to save battery power.
Your computer's hardware configuration or screen resolution was changed. If you changed your screen resolution, video card, or monitor setup, your computer might no longer meet the minimum recommendations for running Aero themes.
Your computer doesn't have enough memory to run all of the programs that you have open and also run an Aero theme. If Windows automatically changed your theme to the Basic theme, and you want to change it back to an Aero theme, close some windows to free up memory, and then follow the steps below.
If the troubleshooter doesn't fix the problem, try changing the theme back to an Aero theme.
Open Appearance Settings by clicking the Start button and then clicking Control Panel. In the search box, type window color, and then click Change window colors and metrics.
Under Aero Themes, click a theme to apply it to your desktop.
To try to get visual elements like transparency running again, use the Aero troubleshooter, which can find and fix problems automatically.
Open the Aero troubleshooter by clicking the Start button , and then clicking Control Panel. In the search box, type Troubleshooter, click Troubleshooting, and then, under Appearance and Personalization, click Display Aero desktop effects.
If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
To learn more about the Windows 7 desktop features that use Aero elements, see What is the Aero desktop experience?