Simplify the following text for a Grade 5 native English-speaking person.
Original: XP may continue to be available as these sources run through their inventory or by purchasing Windows 7 Ultimate , Windows 7 Pro , Windows Vista Ultimate or Windows Vista Business , and then downgrading to Windows XP .
Simplified: XP came after Windows 2000 and Windows Me . It was replaced by Windows Vista which was also replaced by Windows 7 .