It does not make sense to me, data has already been written -- unencrypted -- to C:\ so how can it retroactively change existing data? Does it simply make a copy and delete the original? I thought about that, but wouldn't that require an equal or greater ratio of free:used space? Wouldn't there also be the potential for recovery?
Does it only apply to new newly created files? Almost all encryption programs require you to create a new partition/container.