Sorry, but...

[sky s]

Which WoW do i buy?

World of Warcraft or World of Warcraft Battlechest
the one i want is the one elkaa etc has..
which one is this?

[j]

Just regular World of Warcraft.

http://www.wow-europe.com/en/downloads/classic/index.html

Scroll to regular downloader.
Then choose english and click the "PC" icon.

I downloaded that on got full version of the game basically free..

Only thing needed is a authentic code from the discs, you still need to buy membership though :).