……
ver |find " 6.0">nul &&set TheOS=Vista
rem ver|find /i " 5.0">nul &&set TheOS=2000
ver |find " 5.1">nul &&set TheOS=XP
ver |find " 5.2">nul &&set TheOS=2003
if !TheOS! equ XP set mfile=mountvol_xp.exe
if !TheOS! equ Vista set mfile=mountvol_vs.exe
if !TheOS! equ 2003 set mfile=mountvol_03.exe
……