The number one reason that people select Windows over UNIX is that they know nothing about UNIX and cannot support or maintain it. Windows people administer windows boxes and UNIX people administer UNIX boxes. If you are not familiar with windows servers (even if your familiar with Windows desktops) then it really doesn't matter. Unix isn't as hard as most people think and you probably will have to call an outside contractor either way. Otherwise don't even think about running a server your firm cannot support. Unix (especially Linux) might be cheaper and windows might seem like an easier option. However if it cannot be maintained the business objectives will not be met and it will cost more than you can imagine. When it breaks the staff cannot fix it; and routine work suddenly becomes difficult.