Problem with SQL connection, error: 26 - Error Locating Server/Instance Specified

I am using Windows 7 Ultimate, Visual Studio 2010 and SQL server 2008 on my PC.

I build a simple SQL database program with Visual Basic 2010 on my pc and it run smoothly,

but when I distributed the program to others PC on the same network I got error26 - Error Locating Server/Instance Specified.

I have followed the steps in this article :

http://blogs.msdn.com/b/sql_protocols/archive/2007/05/13/sql-network-interfaces-error-26-error-locating-server-instance-specified.aspx

but the program still could not connect to my SQL Server if run from other PC.

When I use the portqry tools I got this report:

UDP port 1434 (ms-sql-m service): NOT LISTENING

I have disabled windows firewall.

Just could not figure it out what went wrong and really appreciate it if someone can help me solve this.

Thanks.