DWMSM provides part of the new Windows Themes and reverts back to basic styles when running applications that are not compatible with Windows 7. It also performs functions such as the thumbnail view from the task bar and alt+tab, as well as the transparency effects on various windows. If you do not use these functions or your system cannot perform well enough for the new Windows 7 interface, you can disable this service. If you decide to disable this service, you might check into also disabling the Themes service to make it look more like classic Windows 2000 (or XP with its theme service disabled).
