This post talk a bit about the changes to deployment in Windows 7: Windows Setup: You can’t install the beta without using Windows setup (at least once) and we made some minor changes to setup in Windows 7. Note that Minor doesn’t mean insignificant in either effort or impact.
In Windows 7 we moved the license key to the Windows Welcome page, so you can enter it after the install. This makes it easier for people to evaluate and get started with Windows. We also provide a better experience when upgrading editions (i.e., from Home Premium to Ultimate) by enabling specific, licensed components, not reimaging the system.