When first booting a new Sony Vaio laptop (VPCEB2E1E/WI), I had to make a language choice (it warned me that this choice would be irreversible). Since this seems to be just software, I wonder how that's irreversible... and I'd really like to undo my choice. Any hints?
From the wording of the question I'd say that Windows is pre-installed with multiple language options. When you select a language it does "some magic" under the hood finalizing the installation, probably at least deleting the extra language files, etc.
Some sources say that it's possible to change the initial langage selection but it takes quite a bit manual work. The easiest way is to re-install Windows completely, but I'm not sure if the restoration copy that can be burned to DVD after installation is enough, or would one need a fresh (full) copy of Windows.