In troubleshooting a SBS 2003 Server, it was discovered that the system drive was almost out of space.  Upon further investigation, most of the disk space was being consumed in the %WINDIR%\Installer folder.  In that folder were numerous MSI files that were over 100 MB each over and over. 

It was noted that earlier in the week, an update for Backup Exec kept trying to install and failed until the server was rebooted by the customer.  After rebooting the server, the install took, but all of those failed attempts seemingly left these orphaned MSI files created each hour the server tried to install the update.

In order to clean out the orphaned files in this folder, you will need to run “MSIZAP.exe T!”.  You can obtain the MSIZAP file from:;en-us;290301.  Syntax for running MSIZAP can also be found here: [more]

After running this program, it deleted over half of the files in the Installer directory and reclaimed approximately 10 GB of hard disk space.  It was noted that the duplicate 100 MB+ files were removed.