IMHO, while Microsoft doesn't seem to want to own to it, the DWM (Desktop Window Manager) has resource issues. It’s been my experience that the service, essential to the Aero-glass appearance on Windows 7, can easily be “maxed out” if there is too much pixel real estate in front of you. My current environment uses two dedicated graphics adapters (AMD HD 5450 and AMD HD 6450) for 3 1600x1200 monitors. And the Aero-glass appearance can only be maintained for a short time before the system automatically shifts to “Basic” appearance mode (and a varienty of Event ID errors, 9024/9025/9026, are logged in the Application log). Restarting the DWM service re-enables the Aero-glass mode, but that will only last a short time. Would I be correct in assuming that you, too, have large screen space?
The Internet is populated with lots of complaints about DWM, all from people with lots of monitor space (very large monitor, multiple monitors, low-end or high-end graphic adapters). Many are running x64 and have lots of RAM, but the issue keeps popping up. The common thread that I see is that they all have very large total screen space in front of them.
My wife’s machine, conversely, never has issues with Aero-glass. But she only has a single 1280x1024 monitor in front of her, and the critical resources used are much less.
You can get an idea of the resources being exhausted through Microsoft’s SysInternal’s Process Explorer tool; a tool which provides far greater details about each Window's process and is available as a free download from technet.microsoft.com/en-us/sysinternals/bb896653
. Once running this tool, select the dwm.exe process, right-click for Properties, then select the GPU Graph
option. You will see how close to maximum the resources are for this service.