Someone asked a similar question here: http://social.technet.microsoft.com/Forums/en-US/mdt/thread/5731ae3f-1802-4922-9a4f-87e48b2c2f8b
Basically, WDS can deploy images and OSes via the network, which allows you to do network boots and OS deployments through the network. The problem is that WDS can only push images - meaning that any types of drivers, or applications, or configurations
you want to include with the deployment have to be embedded in the image itself, or they won't deploy.
MDT fixes that through scripts and commands that it runs before and after the OS install, to install drivers, applications, customizations -- basically anything you need to include to get a machine to the point where it is basically ready to go - no further
installs or configuration is needed.
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