When you use MDT to deploy Windows 7, you have to create the OS image, called a WinPE. You boot from the WinPE, then run its installation program; WinPE can be booted from a CD, DVD, external hard drive, or WDS server. To boot from a WDS server, hold F12 when starting up the client PC; this creates a Trivial FTP connection to the WDS server's UNC share. Choose WinPE, and MDT installs the OS image on the client.
You can also use WDS with MDS if you want to multicast the OS image (MDT supports only unicasting, or one-to-one connections between the server and a client). By telling MDT to use the WDS multicast protocol, WDS sends the WinPE image to multiple clients, and MDT runs the WinPE image at each client.
Considering virtualized desktop deployment
Windows 7 offers a wild new deployment option: client-side virtualization. You might consider this type of installation because of the flexibility and speed it offers in restoring, securing, and upgrading systems.
One type of client-side virtualization is to install Windows 7 onto a virtualized hard disk (VHD), which is a single file that you can easily copy and deploy anywhere. You can also create incremental VHDs, so you might have a core file that everyone uses and incremental VHDs that have the applications and other configurations for specific departments and even users. The PC boots as normal but opens Windows 7 from the VHD instead of the hard drive's normal file system.
The use of VHDs will slow your PCs by about 3 percent, Microsoft says. It also prevents you from using the Windows Experience Index, as well as BitLocker on the disk where the VHD resides. (You can use BitLocker within the VHD, but not on the disk where the VHD resides.) Note that you need Microsoft's Virtual PC or Virtual Server to create the VHDs, which can run only the 32-bit version of Windows. An MSDN blog details the setup process.
Another virtualization option is the concept of VDI (virtual desktop infrastructure), where the OS is hosted on a server in the datacenter. Users get the same experience as working with Windows 7 directly on their desktop, but IT can manage the desktops locally in the datacenter and even provision them to different desktops, such as when a person is visiting another office or working at home. Gartner estimates that in 2014 about 15 percent of the professional market will run Windows this way.