Since the operation is performed in TCSTART.BTM, one can easily take advantage of the pairing of xxxd.dll and xxx.dll for the language DLL's (model below - use the file exclusion range for languages to be retained):
for /[!EnglishD.dll] %d in (*D.dll) ( set x=%@replace[D.dll,.dll,%d] %+ if NOT %x EQC %d if isfile %x del %x;%d )
This does not account for the language DLL's associated with VIEW.
A recommendation for future versions: provide names for language DLL's that are easily identifiable, e.g. xxx.lang.dll.
Res, would it be possible to have a descriptions of what each file is for, e.g., a DESCRIPT.ION file ?