The SMS 2003 OSD Feature Pack operates in the following five phases:
Validation Phase: This phase is used to make sure that the operating system installation proceeds on the target computer.
State Capture Phase: This phase is used to gather information from the configuration file, databases, and the local machine to determine how the image installation process should proceed. It also checks whether there is enough space to backup the user state locally using the Microsoft Windows User State Migration Tool (USMT) and invokes the USMT ScanState.exe command as appropriate.
Preinstall Phase: This phase is used to confirm that the necessary information has been gathered in the State Capture Phase. It also backs up the computer.
Post Install Phase: This phase is used to update the Sysprep.inf file with information gathered in the previous custom actions.
State Restore Phase: This phase is used to invoke the USMT LoadState.exe command to restore the user state that was previously backed up.