Ryan,
One of the best os's to use for hosting on windows would be windows 2003 server hands down. If your looking for stability you can definitely get it with windows 2003. Another operating system that makes a good host is windows 2000. Then again you could even utilize windows xp professional for hosting.
Make sure to look into the SPLA license from microsoft. No reason to spend an arm and a leg for hosting, when you can purchase an SPLA (Service Provider License Agreement), which will allow you to literally rent the license per month for how long the license is used for web hosting. It is a tedious process trying to be verified for SPLA so bring your lazy boy chair, you in for a ride.
