If you are running the original version of Microsoft Deployment with System Center Configuration Manager 2007 and are looking to upgrade to MDT 2008, here are the basic steps that you need to follow:
Now at this point, all existing task sequences continue to work and are unchanged. For any new task sequences that you create, you should create a new MDT tools package to use with those new task sequences. (If you want, you can update existing task sequences to use the new MDT tools package too, but you'll have to create a new task sequence before you can do that since there's no way to just create a new MDT tools package.)
MDT 2008 does not require Windows AIK 1.1 if you are using only Windows Vista RTM or Windows XP; Windows AIK 1.0 is fine for these. But if you are using Windows Vista SP1, you need to upgrade to Windows AIK 1.1. (If you don't, as soon as you add a Windows Vista SP1 image, you'll start seeing warning dialogs. They won't go away until you do upgrade.) The steps needed to upgrade to Windows AIK 1.1 are:
When Windows AIK 1.1 is installed on the computer that you are using to run the ConfigMgr console, then the MDT "Import Microsoft Deployment task sequence" wizard will create Windows PE 2.1 boot images (instead of the Windows PE 2.0 boot images created from Windows AIK 1.0).
The ConfigMgr team is working on instructions for installing Windows AIK 1.1 for use with ConfigMgr 2007. The basic steps above shouldn't cause any issues (uninstall, reboot, install), but there are some additional steps needed to replace the existing default boot images that ConfigMgr 2007 created when it was first installed. (To move to ConfigMgr 2007 SP1, Windows AIK 1.1, or more specifically Windows PE 2.1,will be required.)