1. There is some proprietary windows only software required for there job (with no open source Linux equivalent)
2. Some computer services they use only support windows (such as NetFlix Instant watch)
3. Their still figuring this Linux thing out
4. They like to play the occasional computer game designed only for windows

2 and 4 apply to me; I still like to play Computer Games when I have a lot of down time, and I subscribe to NetFlix.
Whatever the case, in these situations it is nise to have hard drive space which is shared between both Windows and Linux (I am not going to go into detail about how to partition). I have a large NTFS partition for my documents and media files. In order to make it accessible to Linux I have it mounted automatically.

First thing is to install NTFS-3g which allows for manipulation of NTFS partitions within Linux

sudo apt-get install ntfs-3g

The next step is to make a directory where you want your drive to mount

sudo mkdir /mnt/windows

Now you are ready to edit /etc/fstab

/dev/sda1  /mnt/windows  ntfs-3g  defaults  0 0

the above line can be added to the bottom of the file. Be sure to replace /dev/sda1 with your particular partition. Save the file and reboot. Once your back:

cd /mnt/windows
ls

if you can see a list of files on your NTFS partition and you test if you have write permissions, the processes was successful.