Connect the unit to the computer but do not start Home. Open Windows Explorer. In Explorer, you should see the TomTom unit as an external drive. Click on the unit (drive) so that you see the contents. Do a Control-A to highlight all the contents. Now, a Ctl-C to copy all the contents. Now, move to a folder you've created on your hard drive. Name it something meaningful like TTBackup-9-21. Now do a Ctl-V to paste all the files into your backup folder. That's it.
Well, almost...........
You want to ensure that all hidden files/folders are showing as are extensions for known file types before you do your Ctl-A. How do you do that? By going into Start-->Settings-->Control Panel on your computer-->Folder Options-->In the Advanced Settings window, make sure the choices for Show hidden files and folders is selected (about the 7th item down) and right below it should be 'Hide Extension...". Make sure that selection is UNCHECHECKED.
That's the process. Copying the unit's contents takes only a couple of minutes and is much more reliable than Home's backup method.