first of all, i finally found the solution for this problem.

first is download Microsoft SQL Management Studio Express here. install and run Management Studio Express. Log in using windows authentication.

you can add users there and use this connectionstring in any programming language. mine is classic asp / vb

Driver={SQL Native Client};Server=COMPUTERNAME\SQLEXPRESS;Database=databasename;Uid=username;Pwd=password;

if you are using vs.net 2005, you can simply use windows authentication. there is a video on this in http://msdn.microsoft.com/.

if you are using SQL express... dont forget to add \SQLEXPRESS before the COMPUTERNAME (eg. COMPUTERNAME\SQLEXPRESS)

goodluck!