I agree with the above member, you should look into UBCD4Win and the others.
The only image I see MS mentioning is the AIK image, which they're basically just telling you to burn the image, then install it. You're compiling a set of folders, with tools in them in their appropriate folders, then using a utility to combine those folders into a burnable image. If I understand correctly, what you're asking is 'How to add to an existing image?'
