I came across a system that was running very low on disk space. Disk cleanup utility scans did not offer much to remove, even with system files checked. When I looked at the drive with a graphical utility, I could see that a big chunk of space was being consumed in C:\Windows\Installer.
I came across a very useful utility called "PatchCleaner" which can be downloaded free from https://www.homedev.com.au/Free/PatchCleaner . When it runs, it will give you the results about how many patch files are in use and how many are orphaned.
From there, you have 2 options in the program. Either move the unneeded files to another drive or delete them altogether. I elected to move the patch files first and observed that it moved MSP patch install files. It freed up many GB of space.