Microsoft have updated their MSIZAP utility to include an option to delete cached MSIs
- I would suggest you use MSIZAP instead of my utility..

MSIZAP G = remove orphaned cached Windows Installer data files (for all users)

Visit MSDN for information on MSIZAP

However, if you like living dangerously...

When MSI scripts are installed, a cached copy of the .MSI file is written to C:\WINNT\Installer.
- These files are for repair and self-healing purposes.

If you have a situation where you have a large script that you install, then upgrade every month
(OAG TIS at 120Mb) you may discover you have a large number of redundant cached MSI files.
In our case, after a year of OAG TIS updates, there is over 1GB of cached .MSI files that are just wasting space.

When an MSI script is un-installed, the cached .MSI is left in the C:\WINNT\Installer directory.

This Wise InstallMaster program checks the registry for known cached .MSI files,
it checks the C:\WINNT\Installer directory for .MSI files,
it compares the two lists and deletes any .MSI files that are not marked as 'cached' in the registry.

Note - this does not include transform files - for my purposes, transforms are always very small and so not not take up excessive disk space (something for V2)

Download the zipped program delmsi.zip (includes source code).

Download just the source code.