How do I know which version of Windows I am running?

You can use ${windows_os_version_number}, the values will be:

• 4.0: Windows 95
• 4.1: Windows 98
• 5.0: Windows 2000
• 5.1: Windows XP
• 5.2: Windows 2003, Windows XP 64 bits
• 6.0: Windows Vista