Windows 7
Windows XP
Windows 8
Windows ME / 2000
Windows 98
Windows 95
Windows Vista
That is what I would choose. I put Windows 7 first because it defiantly looks a lot better, and as soon as you get used to it, it has many more features. Windows Vista is going at the bottom because I used to have it on my laptop and it came with it, and right from the start I didn't like it, I only got windows 7 last Christmas.