It depends...

What type of security are you using? Are you using the .NET Data Provider (you should be) or something else? There are other things to consider. See http://www.connectionstrings.com/sql-server-2008

>I want to ask how can i conecct to the slq server properly through visual basic net
>my pcname is PC1
>I have SQL SERVER 2000, SQL SERVER 2005, SQL SERVER EXPRESS 2008.
>when they ask me to enter the server name, what should i enter ? for example
>if it is sql server 2005
> .PC\SQLSERVER2005
>is that correct?
>Thank you in advance
>Luis