>>>Ed,
>>>
>>>Could GetVersionEx() be of any use here?
>>
>>Distinguishing between NT versions, no, since the code base is identical, and the extended OSVERSIONINFOEX structure is only implemented in Win2K. Take a look at the MSDN doc for the lpVersionInfo parameter to see what has to be done differently.
>
>I was thinking about the szCSDVersion member of OSVERSIONINFO structure. I hadn't looked at that member yet and thought you might have.

From the MSDN:

szCSDVersion
Windows NT/2000: Contains a null-terminated string, such as "Service Pack 3", that indicates the latest Service Pack installed on the system. If no Service Pack has been installed, the string is empty.
Windows 95/98: Contains a null-terminated string that provides arbitrary additional information about the operating system.