Last post, I had a problem with transferring addon settings between PC's; using the curse premium client.
I think I have solved my problem; and I tried a few different options.
Now, the addon settings (on my XP pc at least) are in C:\Program Files\World of Warcraft\WTF\Account\AccountId; with one folder per game account you have. (Our household has 3 different WoW players, so many of the PC's have 3 different folders).
Also; both backing up and restoring WoW files are best done when not in WoW.
Option 1: Brute force and massive ignorance. Zip up the WTF\Account\AccountId on the source machine; and mail it to yourself. Mail often has a limit of 10MB; but my zipped up file comes to about 8M. When restoring it; rename the existing AccountId, and unzip the mailed version. This also works well with any file moving method; whether it is a thumb drive or an internet drop box.
Option 2, using the curse premium client. I did something very similar to the above option, but also (for completness sake) moved the C:\Program Files\World of Warcraft\Interface\Addons folder to one side as well, only keeping the addons that started with Blizzard_; then restored all the addons as well as their data files. In reaility this is nearly the same as Option 1, but uses Curse as a dropbox.