WoW

Windows on Windows (often shortened to WoW) is a feature developed by Microsoft that allows 16-bit programs to run in 32-bit environments, or (more commonly) 32-bit programs in 64-bit environments. This means some games designed for 3.x and 9x can be run on any 32-bit versions of Windows. However, software support seems to be very poor and while selecting Windows 95 or Windows 98 in compatibility mode may help, most consider Windows XP to get the best compatibility even though it's unsupported by Microsoft.