I believe i've neglected to mention that all versions (Retail and Download) of E:TW will require the use of the Steam Content Delivery System by Valve Corporation in order to install and play.
The reasons for this are two-fold:
- To enable updates to be installed quickly
- To facilitate multiplayer when the patch containing it is made available
- And, possibly, thirdly, to prevent piracy.
If you do not have Steam, you can obtain it here
, although it is likely that the retail versions will include it on the disc.
It is, however, important to note that you won't have to be online all the time to play E:TW - you can run Steam in 'offline' mode, and still play.
EDIT: This is by no means 'new' information, I simply didn't realise it would affect the retail versions of the game.
The Total War website now has an FAQ regarding STEAM here