Run this command first
http://osxdaily.com/2010/02/03/how-to-prevent-ds_store-file-creation/
Then run this command, then reboot. For good measure run this command again. Also, if you have connected external disk you may want to delete DS_Store files that were created on them by specifying the path and running the command below for each mounted device.
http://osxdaily.com/2012/07/05/delete-all-ds-store-files-from-mac-os-x/