EB requires a clean install of R:TW 1.2, which means no modifications, only the original game plus the 1.2 patch. If you have R:TR and 1.2 in seperate folders, no reinstall is necessary. You can simply EB in the 1.2 folder. However, if they are in the same folder, you will have to uninstall R:TR. I think R:TR comes with its own uninstaller, so it should give you no problem.

If it does, you will need to completely uninstall R:TW, reinstall it and install the 1.2 patch (used the zipped version: it saves you the trouble of cleaning the registry). I would also suggest copying the contents of the patched R:TW map to a new EB map, and install EB in that one. This way you can still install other mods or upgrade R:TW (which is probably going to be necessary for the full EB version ) and the shortcut in the start menu will still refer to the right (e.g. non-EB) version of R:TW.