How does this happen?

Total Annihilation (the first one) had different install screens on all different three computers I installed it on.

Oh, I read your post about the black sphere thing - it might be to do with that kinda stuff. Unless the game happens to have a random selector for the screens you mention, things like that happen a lot in relation to what you described about the sphere.

Often I find weird things to do with different versions of games, TV, movies. Like seeing a version of a film then when you later see it it's very different, and you can't find anything to indicate that it has any alternate versions. Another common one is reading the TV guide listings one day, then reading them again another day (yep, in the exact same magazine) and they are completely changed and there's different shows on. One classic the BBC pulled last year was to show the same film twice in successive weeks and call it a Premiere each time. These things normally work out in my favor so I don't really mention them - in the movie case for example it meant I got to see the film, as the previous week I was watching something else that was on at the same time.

a recent videogame one was when I was playing Tetris Worlds on the PS2 and there were loads more extra Minos (the game chacters, cute fellas), then the game froze and I had to reset the console, when I loaded it again the Minos had different names and different colours........I didn't change anything, like move the memory card or anything like that at all.

I guess it might have to do with the OS I use, the first time it was 98 but it doesnt explain why the last two ones I used are xp Home.