There are four basic desktop deployment scenarios: new, replace, refresh and upgrade . Each can be performed using Microsoft Deployment Toolkit 2010 (MDT 2010), the free deployment Solution Accelerator available from Microsoft  that can be used for both manual and automated deployment of Windows 7. MDT 2010 is built upon the Windows Automated Installation Kit 2.0 that includes the User State Migration Tool 4.0 (USMT 4.0), which is needed for the replace and refresh scenarios.
The new computer scenario is the simplest — the hard drive of the computer you are deploying to is wiped, partitioned and formatted. Then Windows is installed on the computer along with any applications the user needs. This scenario is great for new employees because it provides them with a clean system that has a known configuration and is therefore easy to customize and manage. But what about existing users who have computers that are running an older version of Windows? For these users, you can apply one of the other scenarios: replace, refresh or upgrade.
In the replacement scenario, the user's current computer is replaced with a new computer. The challenge here is to make sure that the user's data (documents and other files) and settings (operating system and application customizations) are not lost in the process. First, copy the user's data and settings from the current computer to a shared folder that is temporarily stored on the network. Then install a copy of Windows 7 on the user's new computer. Finally, copy the user's data and settings from the network to the new computer. The user's old computer can then be decommissioned and recycled.
In the refresh scenario, Windows 7 is installed on the user's current computer while the user's data and settings are retained. The refresh scenario makes use of hard-link migration, a new feature of USMT 4.0 that saves the user's data and settings in a hidden location on the computer's hard drive instead of requiring that it be copied to a file share on the network. After this is done, instead of wiping the user's computer, MDT simply deletes the old operating-system files from the computer. Windows 7 is then installed on the computer, and the user data and settings are restored from their hidden location. The whole process is faster than copying the user state to the network and back, especially if the user has a lot of files on the computer. (If you're interested in learning the nitty-gritty details about hard-link migration, you can read more here .)
Finally, the upgrade scenario can be used for moving from Windows Vista to Windows 7 (but not from Windows XP to Windows 7 because that particular upgrade path isn't supported ). Upgrades aren't generally a good idea in business environments because of the risk that misconfigurations and other issues with the current operating system will be preserved in the process. In other words, upgrading a messy system often results in an even messier system. Refresh or replace are much better approaches than in-place upgrades because the resulting system is clean.
Manually performing the refresh computer scenario means manually migrating a user's computer from Windows XP to Windows 7 while maintaining the user's data and settings. Using MDT 2010, begin by configuring the CustomSettings.ini file for your deployment share so that the various pages of the Windows Deployment Wizard are displayed during deployment. (For more information on the CustomSettings.ini file, see “Understanding LTI Configuration Files” in my series of articles on deploying Windows 7.)
Now log on to the user's computer using the default Administrator account, open a command prompt, and type: \\<MDT_server>\<deployment_share>\Scripts\LiteTouch.vbs
This UNC path for your deployment share will start the Windows Deployment Wizard on the computer, which will display a series of prompts that guide you through the deployment process. As Figure 1 shows, the Choose a migration type page displays only one option (Refresh this computer) since upgrades from Windows XP aren't supported.
Figure 1: Performing a manual refresh from Windows XP to Windows 7.
On the Specify where to save your data and settings page, be sure to use the pre-selected option, Automatically determine the location (see Figure 2). This will initiate the hard-link migration method and preclude having to copy the user's state to a network location.
Figure 2: Leave the first option selected to take advantage of hard-link migration.
Then click through the rest of the wizard pages, sit back, and let MDT do its magic.
To automate the refresh computer scenario, simply include the line DeploymentType=REFRFSH in the CustomSettings.ini file.
Then, to completely automate the deployment, configure the remaining lines in your CustomSettings.ini file to hide all pages of the Windows Deployment Wizard. Log on to the user's computer using the default Administrator account, open a command prompt, and type \\<MDT_server>\<deployment_share>\Scripts\LiteTouch.vbs. In this scenario, however, there will be no prompts that require a response. Instead, a progress box will be displayed showing that the user's state (data and settings) are being stored in hidden form as NTFS hard links on the computer's hard drive (see Figure 3):
Figure 3: The user's data and settings are being saved as hard-linked files.
Once this is finished, all other files on the hard drive will be erased. Windows 7 will then be deployed, along with any applications, packages, drivers or other customizations you specified using MDT. Finally, once everything has been installed on the computer, the user's data and settings will be moved from their hard links to their final locations on the drive (see Figure 4):
Figure 4: The user's data and settings are being migrated to their final location.
The replacement scenario is a good choice if you can afford to purchase new computers for your users. If your budget is constrained, however, and if your existing computers have sufficient hardware to properly run Windows 7, you can use the refresh scenario instead of replace to migrate your desktop computers from Windows XP to Windows 7. To determine whether a particular computer can support running Windows 7, use the Windows 7 Upgrade Advisor . If you're considering refreshing several older computers, use the Microsoft Assessment and Planning Tool 4.0 (MAP 4.0)  instead to determine your organization's migration readiness.