I need know how to format a Kingston memory device

If you delete the files using a file manager, it is probable that the files are actually moved into the trash bin (something like this: .Trash-username ).
This folder is hidden in the file manager. If you wish to permanently delete the files try SHIFT+DELETE, or delete them normally and then use a terminal to delete the trash bin manually.

To check if this is the problem, just try the following command in a terminal: ls -la /path_to_mounted_device
if the storage device is empty nothing should appear.

cheers

Dear Mister Mouro: I have received your message. Thank you very much. It had let me see something aspects of the problem, but it does not solve it at all. Initially I have a KINGSTON device of 2 Gb, with 725 Mb useless after sending the useless files to the trash.
In the terminal I have issued the command ls -la /path_to_mounted_device that you had recommended me to issue. I have found three files in a folder, but, to my great surprise their total size was only of 53 Mb, and when I used the rm command I received a message of file not found. So I coudn't solve my problem.
My question is if is there any possibility of formatting the device, like one gives format to a new hard disk or a new floppy disk.
I do not know if my message is very clear because my native language is no english but catalan.
If my message is not clear, I can translate it into catalan, obviously, but also in french or spanish
Yours sincerely.
Francesc.

I must have written "some" in the place of "something". Excuse me..
Francesc

Well since this wasn't the problem you can try to create a new filesystem in your card partition (high level formatting):

Under Linux, insert your card in the card reader of your PC. Once it is inserted, you need to figure out the device file for your SD/MMC card in order to be able to access it (you can use mount for that purpose).

After figuring out which device is (lets say /dev/sda1 or /dev(mmca) you can format it in FAT16 or EXT2/3 (the choice depends on the usage you give to the card).

Create a FAT16 filesystem

$ mkdosfs /dev/mmcda

Create a EXT3 filesystem

$ mkfs.ext3 /dev/mmcblk0p2

Regarding you previous answer, if you which to delete the .Trash-username directory, you can use
$rm -fr .Trash*
in order to delete .files you need to specify the full name or a wildcard starting with . -> like .*

hope this helps

Dear Mr Mouro: Thank you.
Francesc