Just in case you actually mean:

"I am trying to use ms-sql as a database...how do I add my JDBC driver to JBoss?"

I would recommend using the jTDS driver available here. Whether you use MS's JDBC driver or you use jTDS, the installation of the driver into JBoss AS is the same.

1.) Put your driver .jar file(s) in: C:\jboss-4.0.2\server\default\lib
(${JBOSS_HOME}\server\default\lib)

2.) Edit portal-ds.xml located at ${JBOSS_HOME}\server\default\deploy
change the contents of this file to something like this:

 <!-- MS SQL Server Datasource using jTDS-->
 <no-tx-datasource>
 <jndi-name>PortalDS</jndi-name>
 <connection-url>jdbc:jtds:sqlserver://myserveraddress:1433/mydatabase</connection-url>
 <driver-class>net.sourceforge.jtds.jdbc.Driver</driver-class>
 <user-name>mydbuser</user-name>
 <password>mydbpassword</password>
 </no-tx-datasource>

if you use MS SQL Server's JDBC driver...read the manual to determine the correct values to use in portal-ds.xml.

Good Luck!