Hi,
You can use jTDS
JDBC driver which is an open source or you also have an option of downloading a type 4 driver from Microsoft's Site for MS-SQL Server from this URL given below.It is only for SQL Server 2000 so if you are using it you can go gor
ithttp://www.microsoft.com/downloads/details.aspx?FamilyID=4F8F2F01-1ED7-4C4D-8F7B-3D47969E66AE&displaylang=en ( You have not specified the version of sql server you are using)
Also there is also a jdbc driver aveConnect 3.1 available for MS-SQL versions 6.5,7.0,SQL Server 2000 but it is not free of cost.It is available on 30 days trial basis.