More than likely the whole reason for this process is the individual doesn't know how to install the OS and is too afraid to try. In such case, shipping the computer is the only surefire way, however even then there are some complications that could come up, first of all the cost to ship everything back and forth goes up, then the possibility of damage may occur. Also it's not uncommon for a card, memory, etc to become partially unseated during shipment which will cause the computer to not boot after it gets back to the friend.
Me personally in this scenario would try to walk the individual through the install on the phone. I've had to do this multiple times before for my parents, their friends, companies, and etc, so I'm kind of used to it. Of course, I would tell them "this part will take about 30 minutes, call me back" when necessary, should happen after you specify the drive/partition to install to when it formats the drive (if it's a new big drive, it'll take ages!) and copies the files to finish the install, and then again after you do the initial setup crap telling it what accessories/applications to install.