Can't connect to SQL Database? Getting Errror....

Hi ..

I have just purchased a Win2003 server from 1and1 and they supply it with SQL Express 2005 per-installed...   

I have an ASP.NET application, that I have had running perfectly well locally and on a different VPS with no problems?  I have just uploaded my site (The SQL database is in the App_Data folder off the root of the .NET website) and received this error??

An error has occurred while establishing a connection to the server.  When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Can anyone point me in the right direction as to how to resolve this please, I am very much a novice when it comes to administering SQL on the server

Many thanks in advance