I believe (please correct me if this is wrong) that Windows never actually
supported any of the UCS-2 code that were in conflict with UTF-16. The cost
of this operation was that some of the "private" code blocks of unicode 2.0, i.e. U+D800..U+DFFF were redefined as "surrogates" in Unicode 3.0 making the UTF-16 encoding more or less backwards compatible with UCS-2. And it's UTF-16LE and UCS-2LE, but I suspect you knew that :-)