PatchCleaner is a utility designed to clean up Windows Installer directory and free up disk space. When applications are installed and updated on the Windows Operating System a hidden directory "c:\Windows\Installer" is used to store the installer (.
msi) files and the patch (msp) files. These files are important as during updating, patching or uninstalling software. If you blanketly delete all the files in this folder, you will find yourself needing to rebuild windows. Over time as your computer is patched and patched again, these installer files become outdated and orphaned. They are no longer required, but they can take up many gigabytes of data. PatchCleaner identifies these redundant/orphaned files and allows you to either, move them to another location; or Delete them. You will reclaim GB's of space. Most users of older machines reclaim between 5Gb and 10Gb, the best I have seen reported is over 20 Gb.