New
#11
Factory Recovery will restore eveything to exactly how it came from the factory.
The choice of a D partition is for those who want their data partition separate from the OS to keep the OS backup image smaller. They often keep their data on D and link it to the related Library - Include a Folder - Windows 7 Forums . So if you back up your data in Documents, Pictures, Music, etc. externally then after Recovery instead of copying them back into their folders on C, you would paste the folders to D and then link them according to the blue link.
But you should make Recovery Disks to use as a backup because running Recovery from boot can fail. You need the disks as a backup, or you'll have to order them from Asus Support.
A third option is to get a superior Clean Reinstall - Factory OEM Windows 7.
In the tutorial there are recommendations as well for maintaining Win7 based on what's worked best since before the OS was released.