Most likely there is an updated version on your CDs.
WoW has undergone now 12 major content patches. The patch files on installation are currently 1,8 GB big!
I think, if Blizzard produces new client CDs, they integrate a more recnt version than the 1.0 client.
When did you bought your WoW and whats the version after installation?
Btw. i think the most sensible way of backing up WoW is
1.) install the game (can take quite a while)
2.) update the game to the latest version (can last even longer)
3.) (optional) install all your favorite AddOns (can last forever
)
4.) burn the whole World of Warcraft directory on DVD. Either on a DVD9 or create a multivolume archive using Winrar and spread it across 2 DVD5s.
WoW does not need any registry entries whatsoever, so you can install it simply be placing the files on the computer you want to play. Also the Blizzard updater and the downloaded client patches do not need any reg-entries. Just place them into your installation dir.