Как определить версию операционной системы (Win95/Win98/NT)

Public Type OSVERSIONINFO
  dwOSVersionInfoSize As Long
  dwMajorVersion As Long
  dwMinorVersion As Long
  dwBuildNumber As Long
  dwPlatformId As Long
  szCSDVersion As String * 128
End Type

Public Const VER_PLATFORM_WIN32s = 0
Public Const VER_PLATFORM_WIN32_WINDOWS = 1
Public Const VER_PLATFORM_WIN32_NT = 2

Declare Function GetVersionEx Lib "kernel32" Alias "GetVersionExA" (lpVersionInformation As OSVERSIONINFO) As Long

Public Function IsWindowsNT() As Boolean
  Dim osvi As OSVERSIONINFO
  osvi.dwOSVersionInfoSize = Len(osvi)
  GetVersionEx osvi
  IsWindowsNT = (osvi.dwPlatformId = VER_PLATFORM_WIN32_NT)
End Function

Public Function IsWindows98() As Boolean
  Dim osvi As OSVERSIONINFO
  osvi.dwOSVersionInfoSize = Len(osvi)
  GetVersionEx osvi
  IsWindows98 = (osvi.dwPlatformId = VER_PLATFORM_WIN32_WINDOWS And osvi.dwMinorVersion >= 10 And osvi.dwMajorVersion = 4)
End Function

Использование:

bWindowsNT = IsWindowsNT() ' True, если установлена NT
bWindows98 = IsWindows98()   ' True, если установлена Windows98