1 , first with Window login authentication mode in, select the database instance, select properties - Security: Server Authentication option from the "Window Authentication Mode " changed to "SQLServer and Window Authentication mode " . Click OK to close the current Object Explorer.
2 , re-use Window authentication login, select the tree structure on the left " database " following " Security " option - login --sa , right attributes - the "SQLServer authentication " Enter to set the sa password.
3 , restart SQLServer service. Remember, restart the service is not turned off sqlserver2008 then on.
具体方法是在数据库实例上点右键，选择“重新启动”项即可。最后关闭sql server2008，启动后用sa登陆。
如果忘记了sa的登录密码，可以先用windows身份认证登录进去，然后新建查询，输入命令：
EXECUTE sp_password NULL,'输入新密码','sa'
设置sa新的密码，然后就可以用sa用户名进行SQL Server登录了。
另外，在获得管理员权限的情况下，可以用命令行添加SQL用户、先建立一个c: est.qry文件,内容如下:
exec master.dbo.sp_addlogin test,123
EXEC sp_addsrvrolemember test, sysadmin
然后在DOS下执行:cmd.exe /c isql -E /U alma /P/ic: est.qry
