Colin (and others)
FTM has two file formats.
.FTM is the operating file. This file can have links to media from either their individuals locations on your hard drive, or linked to copies on the media center. FTM gives you a choice which way you want to work. I use the media center.
The second format is .FTMB (B meaning backup) (By the way there is no .FTMDB file format)
This is created when you do a File>Backup in FTM. This creates a compressed version of the .FTM file, (it is actually a .ZIP file [Winzip], but with the extension .FTMB). (As an aside you can rename an .FTMB file to a .ZIP file and expand it with Winzip).
Now there are two options when you back up
1. You can just backup your .FTM file; or
2. You can backup your .FTM file and also back up all the media linked to it.
In both cases the backup file is a compressed file and that is why you have to do a File>Restore if you want to expand an use a .FTMB file
Let me give you an example
My .FTM file is about 24 MB
If I back it up to .FTMB (File>Backup and DO NOT INCLUDE ANY MEDIA, the backup file size is about 6 MB
So the backup (zip) process has reduced my file to about 25% of its expanded size.
With me so far?
Now I have 237 media items linked to the file. These are a mixture of TIF, JPG and GIF files and in total the size of the folder with the 237 media files is 436 MB.
Now if I back up my FTM file and the media files as well, the size of the combined media and FTM files (an .FTMB file) is 413 MB. Media files don’t compress all that well.
In essence you need not worry about much, FTM does the work
If you want to backup your FTM file, simply do a File>Backup (tick all the boxes, media, favourites and historical events) and let FTM do the rest. Save the combined .FTMB is a safe place, (not on your working C: drive).
Back up regularly especially if you have done a lot of editing
Also be aware that you can and should compress your .FTM file regularly with the Tools>Compact function. This will reduce the size of your .FTM file
I also suggest that if you are unsure of anything, create a dummy or test file (use an old file etc) and practice backing up and more importantly doing a File>Restore and check that you get everything back. Best to practice this before you really need it.
You might find this article on the FTM Knowledge Base with it screen shots also usefulhttp://ftm.custhelp.com/app/answers/detail/a_id/4378/kw/back...