Prestart hooks (previously known in CM07 as pre-execution hooks) are used to allow the admin to perform additional steps prior to the start of the TS, such as capturing the username and prompting the user to input data. Prestart hooks can be used at the beginning of the TS to prompt the user for information, or programmatically determine information that applies to the OS deployment process. For example, you could prompt the user to select a location, or additional components to install during the TS. You could also query a web service or a database to determine the role of a server to deploy.
CM07 enables you to create prestart hooks by mounting a boot image, and add a .ini file with instructions to launch the desired script or executable. While that process is still available, CM provides two additional methods to configure prestart hooks from the admin console:
On the boot image properties
During the media (USB or ISO) creation process
Prestart...