sorry for reply lately.thanks for your kindly.i had fixed the problem with my friend.actually just a command error when wanna to connect with the server.thanks yea..

the command in .Net should be like this to connect to the server for my pc(but my friend can use the athoher command to access the server).

SqlConnection conn = new SqlConnection( "server=(local)\\NETSDK;" +
"Integrated Security=SSPI;" +
"database=UserAccount");

thanks