Microsoft published new guide about custom reports in System Center Configuration Manager 2007. Documentation package “Creating Custom Reports By Using Configuration Manager 2007 SQL Views” is now available for download: http://www.microsoft.com/downloads/details.aspx?FamilyId=87BBE64E-5439-4FC8-BECC-DEB372A40F4A&displaylang=en
 
Package CreatingCustomReportsByUsingSQLViews.msi includes the following files:

Before You Use – Readme document (BeforeYouUse_Readme.doc)
Using Configuration Manager 2007 SQL Views to Create Custom Reports help file (CM2007CustomReports.chm)
Configuration Manager [...]

When you want to create a custom report in System Center Configuration Manager 2007 you can use existing objects in SQL SCMM database or you can create? new SQL objects using SQL Server Management Studio.
 

1. Create a new SQL object

Open SQL Server Management Studio
Use Object Explorer: [Server name] > Databases > [SCCM Database] > [...]