Distinguish between different Windows versions
1. Check if Environment.OSVesion.Platform returns WIN32NT (for Win3.1, Win95, Win98, WinME) or WIN32Windows (for WinNT and later) or WinCE (for Windos Mobile etc.)
2. Check version from Envirnement.OSVersion.Version
Win95: 4.0
Win98: 4.10
WinME: 4.90
NT 3.5: 3.51
NT 4.0: 4.0
Win2000: 5.0
WinXP: 5.1
Win2000: 5.2
Vista/Windows Server 2008: 6.0
Windows Mobile 5: Windows CE 5.1
Windows Mobile 6: Windows CE 5.2
Reference: