Is dwm.exe is a virus?how to disable the dwm.exe process in windows7

Desktop Window Manager (dwm.exe) is the window manager that gives you effects like transparent windows, live taskbar thumbnails, quick re-size and preview, flip feature and many more in Windows Vista And 7.It's not a virus!
But It consumes most of memory (approximately 55MB per windows,task).

Here are the steps to stop this dwm.exe temporarily without disabling it to speed up your PC
-->Type “Service” into the search box
--> Select the “Service” link
-->Right click on “Desktop Windows Manager Session”
--> Select “Stop” to stop it from running

Disable dwm from startup
--> Double click on “Desktop Windows Manager Session”
--> Select “Disable” as shown in screenshot
-->Click “OK”