java连接sqlserver数据库报错！请帮忙解决

import java.io.*;
import java.sql.*;
public class ConnectionSql{
public static void main(String[] args) throws IOException,ClassNotFoundException

{
String driver = "com.microsoft.jdbc.sqlserver.SQLServerDriver ";
String url = "jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=pubs ";
String user = "sa ";
String pwd = "liyan ";
try {
Class.forName(driver);
Connection conn =DriverManager.getConnection(url,user,pwd);
System.out.println( "数据库连接中.... ");
Statement stmt =conn.createStatement();
ResultSet results =stmt.executeQuery( "select * from titles ");
//int num=1;
while (results.next()) {
String titles =results.getString( "title ");
String type =results.getString( "type ");
System.out.println( "书名: "+titles+ " 价格: "+type );
}
stmt.close();
conn.close();
System.out.println( "连接关闭中... ");
}
catch (SQLException e) {
e.printStackTrace();
}
}
}



出错提示

Exception in thred "main" java.lang.ClassNotFoundException:com.microsoft.jdbc.sqlserver.SQLServerDriver

环境配置
CLASSPATH=.:%JAVA_HOME%\lib:%JAVA_HOME%\jre\lib;%JAVA_HOME%\bin;%JAVA_HOME%\jre\lib\mssqlserver.jar
JAVA_HOME=F:\Program Files\Java\jdk1.6.0_19
PATH=F:\Program Files\Java\jdk1.6.0_19\bin;
请各位大大帮忙看看什么问题