I recently had my system drive go bonkers after a botched AntiVIrus upgrade and had to restore it from an image--one that didn't have XIV installed on it. Fortunately, I had the game running on my laptop also, so I was able to pull the character data over from the My Documents/My Games folder onto the PC, and all the hard game files were still intact on my Data drive.

So, basically all I had to do was run the installer--was the phase4 beta I still had in my archives folder on the Data drive. Directed it to install in the same folder where the hard files still were and it installed without a hitch. Told it I had an existing account and all, and just logged into the game, it downloaded about a 75MB patch, and I started playing.

So, basically all you need to do is save off the entire FFXIV install folder (Program Files (x86)\Square Enix) and your character data (My Documents\My Games... find the FFXIV top folder) to another drive. Grab the FFXIV installer too while you are at it if you still have it on your hard drive. After the restore, copy all those folders back to the original locations, run the installer and tell it to install back in that same folder like it was before, answer the prompts that you have an existing account and such. When you first log in, it will run the version check against the config files and only update if it detects an older version. Since you grabbed the top level folders, you are getting all the version ID files, all the patch files, and all your custom HUD/Character data restored, so when you log into your SE AM account and all, it should synch up like it normally does.

Just be prepared... it won't fit on a single DVD--not even a dual layer one. You will want at least a nearly empty 16GB thumbdrive, as the install directory is running a little over 9GB now.