There was a article on digg on unattended windows setup link . It's a nice article which describes how to create the lasted install disk in addition to how to install windows unattended.
The article has a section where it deescribes how to update the source with the latest hotfixes it describes 3 methods to create a update list. I would like to add two easier methods to get a update list. The first one is a slight variant of the
method 2 mentioned in the original article.
1. Windows update : If you have a machine which is installed using the same service pack say service pack 2 and you have auto updates turned on Then you could got to update.microsoft.com
and view the link review your update history to get a list of all the hotfixes installed till now from windows update.
2. Using Add remove programs: In the add remove programs applet there is a check box show updates which when selected will give the list of updates installed.
Note: I suspect that you will have to have "a machine which is installed using the same service pack number" to get the correct update list.