Operating Systems - Windows, Vista, iOS and zOS
Vista. If you want Windows 7 or 8, buy a new computer.
BTW I use Vista and am very happy with it. Never a problem. Of
course, I never tried to upgrade from XP and never tried to port
software from XP to Vista. Don't do that.
If you want upwards capability, then get a mainframe. IBM Mainframes
are very good at compatability to previous versions. Some are still
running code that was written in the 60's and 70's. Really.