How do you install ubuntu linux on your PC WITHOUT gettig rid of Windows Vista or XP?

Okay, I would like to have linux and Windows Vista both running on one machine. I DON’T want to get rid of Windows Vista, so what do I do after I download linux. I would also like to do the same with XP too.

And please NO bad mouthing about windows or windows vista. I happen to like Microsoft and Windows Vista and I DON’T want to get rid of it.