If you need to use Windows, install it first, then Linux. Most flavors of Linux will set-up dual booting for you with little hassle. Call Microsoft and explain what happened and get them to walk you through the issue. This, of course, assumes that you have a valid copy of Windows.
What I recommend you do for Linux is try a Live CD version of Linux. Most Linux distros (flavors) have a live CD version that allows you to "test drive" it before you install it on the hard drive. This way, you can see if the Linux flavor that you pick is user friendly for you and your roommate.
Mepis or Mandriva would be good starters to do this.
Of course, make sure that you have hardware that is compatible with any Linux flavor that you choose. Knowing what make and model system that you have would help folks guide you in this respect.
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"I love it when a plan comes together." - Hannibal Smith