I have been using a flash drive to transfer image files from my OLD PC (Windows) to my iMac.  I deleted the files on the flash drive after copying them to iPhoto and found that the freed up memory was still not available although the drive showed EMPTY in Finder.

I note that on the Mac OS we don't have a system of "hidden files" so I plugged the flash drive back into the PC and chose "show hidden files".  LO and Behold! There appeared two folders labelled "Trashes" and one labelled "Spotlight", containing all the missing memory.  I deleted these folders whilst on the PC and recovered the memory.

So! this is the question; how do I delete files completely from the flash drive on the iMac?

On selecting "Get Info" (the flash drive now back in the iMac), and bringing up the information box on the flash drive, it informs me that the drive format is MS-DOS(FAT16); so is that the problem?  And if so, can the flash drive be reformatted?  And if it can be reformatted to Mac OS Extended (Journaled) will it still be useable on the PC?

I look forward to being enlightened.

jayessJayess,

Yes, there are hidden files on macs just like on Windows machines.

You can, in fact, reformat the flash drive to wipe it completely.  In order to do this, open up "disk utility."  (You can find this application on your mac under Applications --> Utilities --> Disk Utility)

Once Disk Utility is open, just click on your flash drive on the left hand side, then click on "erase" on the right side.  This will bring up a menu allowing you to rename the flash drive and choose how it's formatted. 

NOTE:  If you WANT to use this with your windows machine, you'll want to format it as MS-DOS (FAT).  You cannot see a Mac OS Extended (Journaled) partition on a windows machine.I forgot to mention one other item.

You can also disable spotlight from ever indexing your flash drive.  Simply click on spotlight in the top right corner, then choose "Spotlight Preferences."

In there you can tell spotlight what NOT to index.  This is helpful for smaller flash drives, as it wont' take up any space on your drive for that.

As far as the trash goes, simply make sure that you empty the trash before ejecting your flash drive and it will empty the "trashes" FOLDER on your flash drive.Socrates,
Thank you again for your assistance. Problem solved!
jayessNo problem!