The Common Lisp function software-type returns a generic name for the Operating System. The Common Lisp function software-version returns information about the version of the Operating System.
In particular software-type cannot be used to distinguish between different versions of Windows, whereas software-version allows you to identify variants such as Windows Vista, Windows 7, Windows 8, Windows 10 and so on. See the manual pages for details.
LispWorks User Guide and Reference Manual - 20 Sep 2017