If you want to turn on Check Spelling for English in a localized version of WLW, please read this post.
http://jtbworld.blogspot.com/2007/06/windows-live-writer-spell-checking.html
The only change is that you should use WLWSCL.exe to launch Writer instead.
Since the source code is provided, you can learn how to change the default culture of an assembly. Yes, this technique can be applied in many other cases.