I wanted to use Junction Master to move the files in C:\Windows\Installer off of my SSD and onto a normal HD to save space.
When JM complained that there were files in use (on a freshly rebooted / quiet system), I used Unlocker to view what process has open file handles on files in that dir.
It is Explorer.EXE. Why Does Explorer.Exe hold open file handles to files in C:\Windows\Installer ?