If you want to add registry keys or files you need to create new components and features for those.  Refer to the Windows Platform SDK for details.

It is beyond the scope of this document to provide a comprehensive overview of how to add new resources through a transform.  Please refer to the "Windows Installer" documentation for details.  The relevant section is at :

http://msdn.microsoft.com/library/en-us/msi/setup/using_transforms_to_add_resources.asp

A sample walkthrough of adding a new configuration file is in section 2.3.

Add new features under the 'feaClient' or 'feaServer' as appropriate and set the 'Level' column for those features to equal the 'Level' for their parent features for consistency.  Note that none of the features in the OpenAFS for Windows MSI package are designed to be installed to run from 'source' or 'advertised'.  It is recommended that you set 'msidbFeatureAttributesFavorLocal' (0), 'msidbFeatureAttributesFollowParent' (2) and 'msidbFeatureAttributesDisallowAdvertise' (8) attributes for new features.

If you are creating new components, retain the same component GUID when creating new transforms against new releases of the OpenAFS MSI package.

After making the adjustments to the MSI database using ORCA.EXE you can generate a transform with MSITRAN.EXE as follows :

(Modified MSI package is 'openafs-en_US_new.msi' and the original MSI package is 'openafs-en_US.msi'.  Generates transform 'openafs-transform.mst')

    > msitran.exe -g openafs-en_US.msi openafs-en_US_new.msi openafs-transform.mst

See the Platform SDK documentation for information on command line options for MSITRAN.EXE.