Okay, so it’s looking more and more I have to restore a back-up of my hard drive for my Mac. It’s been awhile since I last did a back-up though, and can’t remember if Scrivener is on there or not. Is there a way to save Scrivener to my external HD and reinstall after I use the back-up, or will it that not work? Any suggestions? Thanks.
There’s not a lot of point in backing up an application, in my view. You can just download it from the Internet and reinstall it. There is some point in backing up preference files, particularly if you’ve heavily customised everything. If you look in Preferences there is a drop-down labelled “Manage …” where you can save preferences. You can save layouts, as well – can’t remember if there are any others – have a look in the manual.
As for the data – the projects – you can save those wherever you like, in as many copies as you like. Minimum of three separate copies in three different places is an oft-cited rule of thumb.
Martin.
Just to offer another point of view, I do archive software religiously, in multiple locations just like I would my data—and especially so when my data requires that application to be easily read. My reasoning for doing this is that there is no guarantee that software will forever be available from the Internet, and in fact it would be fair to say that it is certain that one day it will not be available (it may take decades for that to happen, but it will unless the software is one day open-sourced, and even then you never know). I already have about four or five programs that I use fairly regularly, that if I had not had the foresight to archive them, I would no longer have access to, and one of them is rather extremely important as it unlocks thousands of passwords and serial numbers that I own (and is a pain to export from, the joys). Of course, this will never be Scrivener’s fate 
but it’s a good idea to do save downloaded software installers and whatever info you need to unlock them.
To answer the original question: it is best practice to archive the installer not the application. For one the installer will be compressed, so it will take up less space. Secondly it will be archived in single-file format rather than being composed of many thousands of files in folders. So that is what I would do: download the installers and save those.
One rule for geeks, another rule for the rest of us, I think!
Now where’s my copy of LocoScript?
Martin.
Then I’m both a geek and a “rest of us” … I do a bootable back-up to an external drive on a weekly basis, but also store the my installers separately!
Mark