When you watch a video in Windows Vista, video performance may suddenly be reduced. For example, you may notice lost frames or other poor video performance.

This problem occurs if the following conditions are true:

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The system does not support Windows Aero. For example, the computer is running a version of Windows Vista that does not support Windows Aero, such as Windows Vista Home Basic. Or, the video hardware of the computer does not support Windows Aero.

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The video window is partially covered by any of the following Windows elements: • Windows Sidebar. • The Windows Start menu. • A tooltip. • A software pointer that has shadows. • Any window that has rounded corners or other transparent elements. • A window that has shadows. • A sprite that has transparency elements or shadows. A sprite is a two-dimensional image or animation. For example, some Gadgets for Windows Sidebar are sprites.

Video performance decreases only when any of these elements partially cover the video. When the elements no longer partially cover the video, the video plays as expected.

The poor video performance may be more severe on computers that have slower CPU hardware. Other factors that may affect this problem are the display resolution, the random access memory (RAM), the graphics processing unit, the memory bus, and the drivers.

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This problem occurs if the Desktop Windows Manager is disabled. The Desktop Windows Manager is disabled if the system does not support Windows Aero.

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To work around this problem, use one or more of the following methods:

•	Avoid using Windows elements that may partially cover the video while you watch it. For example, do not move the mouse pointer over any area of the video program while you watch a video. By not moving the mouse pointer over the program, you prevent a tooltip from appearing.
•	Close Windows Sidebar. Or, move the video window so that it is not partially covered by Windows Sidebar. To close the Windows Sidebar, right-click Windows Sidebar in the notification area, and then click Exit. To reopen Windows Sidebar, click Start, click All Programs, click Accessories, and then click Windows Sidebar.
•	Turn off shadows. To do this, follow these steps: 1. Click Start, right-click Computer, and then click Properties. 2. Click Advanced System Settings. If you are prompted for an administrator password or confirmation, type your password or click Continue. 3. Click the Advanced tab, and then click Settings in the Performance area. 4. Click to clear the following check boxes, and then click OK: • Show shadows under menus • Show shadows under mouse pointer
•	Make sure that you are using the latest Windows Vista Display Driver Model (WDDM) capable driver for the video hardware. For more information, contact the manufacturer of your hardware. For information about how to contact the manufacturer of your hardware, click the appropriate article number in the following list to view the article in the Microsoft Knowledge Base: 65416 (http://support.microsoft.com/kb/65416/) Hardware and software vendor contact information, A-K 60781 (http://support.microsoft.com/kb/60781/) Hardware and software vendor contact information, L-P 60782 (http://support.microsoft.com/kb/60782/) Hardware and software vendor contact information, Q-Z

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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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For more information about a similar issue, click the following article number to view the article in the Microsoft Knowledge Base: This problem has been reported only on Windows Vista-based computers that do not have Windows Aero enabled. For more information about why Windows Aero may not be enabled, click the following article number to view the article in the Microsoft Knowledge Base: Windows Aero is the premium visual experience of Windows Vista. It features a transparent glass design that uses subtle window animations and new window colors. Part of the Windows Aero experience is Windows Flip 3D. Windows Flip 3D arranges your open windows in a three-dimensional stack that you can quickly flip through without having to click the taskbar. Aero also includes taskbar previews for your open windows. When you point to a taskbar button, you see a thumbnail-sized preview of the window. You see the preview whether the content of the window is a document, a photo, or even a running video.

The following editions of Windows Vista include Aero:

•	Windows Vista Home Premium
•	Windows Vista Ultimate
•	Windows Vista Business
•	Windows Vista Enterprise

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