The C:\Windows\Installer folder contains Windows installer cache, it’s used to store important files for applications installed using the Windows Installer technology and should not be deleted.
The installer cache is used to maintain (remove / update) the applications and patches installed on the computer. The installer files are a record of file versions and registry dependencies involved in a particular application or application update installation. The availability of this record in the cache helps to uninstall and update applications properly.
I have found that the best way is to move/backup those files, and there is a tool made by HomeDev who can do just that and even give you the option to choose between moving the orphaned file or just delete them safely. you can download it from here or directly from this site here .
Another way is to use DSIM