Linux distributions have different flavors in other words files may be placed in different places and one might like certain distros better than others for certain things. That in my opinion is why someone would want to install different distros. As for installing in order always install xp first because if you install linux first there are always more chances that xp will mess up your linux install. Don't know why it happens but it has happened to me a few times. You might want to look at http://www.osloader.com/ It allows you to make it more gui type os loader if you are new to this type of thing.