You need to embrace the buy dont build philosophy. How long do you think it would take for you to create a BB in asp.net that would offer as much functionality as you get right now? Its simple math. If it takes 1 month at $15.00/hr (becuase youre an intern or something) thatll cost $2400. Meanwhile you can use phpBB2 (or others) for free ($0), they actually work (becuase whatever you write will have only been around for a month, other boards have been worked on for years), and its available right now (not a month, oh wait, two months becuase of unforseen difficulties). Even if it did cost money, its bound to be less that $2500.
Its just not economical to write a home grown solution when there are solid solutions already available.