I set a configuration to purge temp files but it doesn't seem to be working?

The problem is... When you open an attachment in Outlook, it automatically saves a copy to the temp folder, if there are multiple attaaachments with the same name, it will append them with a number (voicemail (1).wav... Once it's hit 99, it won't open another voicemail.wave file, so I've manually gone on users machines as this has come up and deleted the temp files. I found the configuration that should do this automatically but it's not deleting anything...

Help please?