Hi,
If you're going from an Admin image, this could be more difficult, since there's not a really clean way of getting the files back into a cab, adjusting file sequence numbers, then streaming the cab into the msi. If you already have *.cab's, though, you could use MsiDb.exe, I think, to stream it in, and then change the Media table to look internally for them:
http://msdn2.microsoft.com/en-us/library/aa370083.aspxFailing all that, you can also open the *.msi in 'Wizard' mode (under the File -> Open dialog of Editor). This will actually create a project file out of the *.msi that you can rebuild. It's quite clever in that regard.
Let me know if you have questions on this.
--Cary