For anybody reading this thread to resolve similar problems, and if you do not get what the conversation is about, it is Ken suggesting that *.mbz fies can be renamed to zip files, unzipped, then edited, rezipped and restored. This is a tried and tested technique that has saved my bacon more than once, but the language used here is difficult for anyone not fluent in geekspeek to follow, it obscures too much. Also, it does not matter if you are using a Linux or Windows server, a local host or anything else, the technique is the same.
The editing comes in two different ways, one is the resources, activities, quizzes, images. video files and so on are listed, written and referred to in the moodle.xml file. You can find the starting point and the end point of each resouce, and Ken provides an example of that, that you can delete out of the xml file. The second part of editing is locating the actual resouce if it is an image, a separate file or video then deleting it. Really large mbz files tend to have a lot of videos, often flv files, or uncompressed images, like tiffs. They can be found, and deleted easily, in the directory tree of the backup.
You can then rezip the edited file, rename it to an mbz and, if you have edited it right, it should restore. You can use the original file to break down really large backups over and over into four or five smaller mbz files, as many as you like.
I would recommend that you test the technique first on a smaller file, it is easier to follow and gets you used to xml structuring and so on. Say one course with a couple of pages, a number of different image types, a couple of videos will help you immensely.
You do not have to worry about permissions on a Windows machine, or concern yourself with editing rights usually.
Thanks to Ken for his detailed explanation.