Why only if you use a gameserver that requires it? MSSQL still is a lot better then MySQL in some ways (such as parametrised queries, subqueries, scheduled jobs, etc.)
Anyway, go see the MuOnline forum, there are plenty of guides there on how to setup your MSSQL server.
(a damn good hint would be the 'import database' thingie btw...)
Closed for obvious reasons.