Are you unable to create uppercase directory name on your storage device mounted as vfat file system. The reason for this behavior is that vfat filesystem is by default mounted by mount command with shortname option set to lower.

Therefore, you nay force your system to mount your disk to show directory names as they are with winnt:
mount -o shortname=winnt /dev/sdb1 /media/temp
Here are couple more options to be complete:
lower Force the short name to lower case upon display; store a long name when the short name is not all upper case. win95 Force the short name to upper case upon display; store a long name when the short name is not all upper case. winnt Display the shortname as is; store a long name when the short name is not all lower case or all upper case. mixed Display the short name as is; store a long name when the short name is not all upper case.
Another solution to this problem is to use pmount. pmount command syntax is little different from the ordinary mount command. Instead of specifying a mount directory as an argument a user needs to specify lable. The lable will be eventually a name of the directory under /media:
# pmount /dev/sdb1 MY_DISK # cd /media/MY_DISK/ /media/MY_DISK# ls MEMSTICK.IND MP_ROOT MSTK_PRO.IND MUSIC PICTURE PSP TEST VIDEO