Atari DOS, several versions on the Atari 800XL and 65XE, MSX basic on my MSX machines, Atari TOS and GEM on the Atari ST machines, Commodore BASIC on my Commodore 64's on the XT machines DOS 5.1 on my 386 I use DOS 5.1 and Windows 3.0 on my 486 machine IBM DOS 2000 and Windows 3.11 for workgroups, on my Pentium 133 I use Puppy Linux which is installed on HDD, on my Pentium 233 MMX and P-II 333 I use Windows 98SE then I have some Pentium II, III and older AMD machines running Windows 2000 Pro, Suse Linux, or Xubuntu Linux my modern machines run either Windows 2000 Pro or Windows XP I do NOT use Vista...