A client of mine recently had CCleaner, a valuable cleaning tool, delete a file that one of his programs (which was poorly designed) needed to run, even though that file was in a temp folder.
The file that it deleted on his system was DAO.msi. So, if this happens to you with a different file, then replace DAO.msi with the name of the file that you are needing to keep on your system.
If this happens to you with this file, or another file, then here is how to tell CCleaner to exclude that file so you can continue to use this valuable cleaning tool: