Sharepoint 2007 and SQL Express

I have just been building a couple of Sharepoint 2007 test servers with SQL Express

I have been seeing the error message

ReporterServer$SQLExpress $ is an illegal charactor.

having removed SQL Express and replaced it with SQL Server the error still persists

however after some gnashing of teeth and toil , the answer is that SQL Express reporting services creates an App Pool of the Name Reporter$SQLExpress which when removed allow Sharepoint to install applications

b.