; GetWindowsVersion
;
; Based on Yazno's function, http://yazno.tripod.com/powerpimpit/
; Updated by Joost Verburg
;
; Returns on top of stack
;
; Windows Version (95, 98, ME, NT x.x, 2000, XP, 2003)
; or
; '' (Unknown Windows Version)
;
; Usage:
;   Call GetWindowsVersion
;   Pop $R0
;   ; at this point $R0 is "NT 4.0" or whatnot

Function GetWindowsVersion

  Push $R0
  Push $R1

  ClearErrors

  ReadRegStr $R0 HKLM \
  "SOFTWARE\Microsoft\Windows NT\CurrentVersion" CurrentVersion

  IfErrors 0 lbl_winnt
  
  ; we are not NT
  ReadRegStr $R0 HKLM \
  "SOFTWARE\Microsoft\Windows\CurrentVersion" VersionNumber

  StrCpy $R1 $R0 1
  StrCmp $R1 '4' 0 lbl_error

  StrCpy $R1 $R0 3

  StrCmp $R1 '4.0' lbl_win32_95
  StrCmp $R1 '4.9' lbl_win32_ME lbl_win32_98

  lbl_win32_95:
    StrCpy $R0 '95'
  Goto lbl_done

  lbl_win32_98:
    StrCpy $R0 '98'
  Goto lbl_done

  lbl_win32_ME:
    StrCpy $R0 'ME'
  Goto lbl_done

  lbl_winnt:

  StrCpy $R1 $R0 1

  StrCmp $R1 '3' lbl_winnt_x
  StrCmp $R1 '4' lbl_winnt_x

  StrCpy $R1 $R0 3

  StrCmp $R1 '5.0' lbl_winnt_2000
  StrCmp $R1 '5.1' lbl_winnt_XP
  StrCmp $R1 '5.2' lbl_winnt_2003 lbl_error

  lbl_winnt_x:
    StrCpy $R0 "NT $R0" 6
  Goto lbl_done

  lbl_winnt_2000:
    Strcpy $R0 '2000'
  Goto lbl_done

  lbl_winnt_XP:
    Strcpy $R0 'XP'
  Goto lbl_done

  lbl_winnt_2003:
    Strcpy $R0 '2003'
  Goto lbl_done

  lbl_error:
    Strcpy $R0 ''
  lbl_done:

  Pop $R1
  Exch $R0

FunctionEnd