一开始management studio可以连通，vs05不行，很是郁闷。
我在网上很不容易地找到这么一段，终于解决了。不光是要开启TCP协议，重启服务，还要设置端口号，动态端口清空，端口号设置为1433，就成了。原理我也不懂。
Under "Protocols for SQLEXPRESS", ensure that
"TCP/IP" is enabled. Double-click on TCP/IP, set Enabled to Yes, and
under the "IP Addresses" tab, clear all the "TCP Dynamic Ports" entries
(set them blank), and set TCP Port (under IP All) to 1433. We are
fixing the port, which means SQL Browser service can be stopped (in
fact, this is a security best practice). You may need to use another
port number if you have other versions/instances of SQL Server running.