Format a pen drive to Fat32

as root:
Linux automatically mounts the device; it should be unmounted but not do it from konqueror because it removes the /dev/... link
>root# mount #It will list all the mounted devices; find the usb drive you want to format
>root# umount /dev/sdbX
>root# mkfs.vfat /dev/sdbx
And that's all ... remove using konqueror and plug again; and you have a clean usb ready to go