I've been programming Windows professionally since 1994. MS has made many claims about backwards compatibility. Not all of them are true.
I did not include WIndows 64-bit because I did not know for sure Chessbd was compatible with it.
Why don't you go do something useful and check for us?
Are you, hereby, claiming that all Win32 applications will work on all Windows 64-bit OSes?
Someone on a forum said the Chessbd was not compatible with Win 64-bit. I didn't check. Considering that Chessbd is an old app originally written for Win 16 that seemed possible.