I have an VB.NET app that connects to a local SQL SERVER EXPRESS database

On the computer I developed the application everything works ok but when I try to deploy the application on another computer with SQL SERVER EXPRESS installed an error message appears : << under the default settings SQL SERVER does not allow remote connections. (provider :SQL Network Interfaces, error 26 : Error Locating Server/Instance Specified) >>

Is it the connection string that is bad or the fact the on my machine I have an SQL SERVER EXPRESS instance named COMPUTER\MYNAME and on the deployment machine I have another instance name