Report Packs And SQL Server Express

I am trying to use the IISLog report packs with SQL Server Express reporting services. The guidance in http://blogs.msdn.com/sqlexpress/ indicates that I need to change the target URL and the connection string so that the report packs work with SQL Express. I cannot see how to centrally change the connection string, so that it will affect all the Datasets in the report project. If I try and open a report page and click on the Data tab I get the following error.

A connection cannot be made to the database.
Set and test the connection string.

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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 2)

I have seen this error before when I have mistakenly used "data source=(local); initial catalog=AdventureWorks" instead of "data source=.SQLExpress; initial catalog=AdventureWorks" as a connection string when creating a new Dataset.

How can I get the IISLog report pack to work with SQL Express?