have you tried sysocmgr ??? - http://www.myitforum.com/articles/15/view.asp?id=8792 - you should be able to do it with that, but may be prompted for installation media. . . which may require some extra tricks...

FYI - the MDT Extensions for ConfigMgr have this built in to the task sequencer, but I think it's only for Server 2003/2008/r2.