if ever the problem shows up......
Q: I've been copying my Excel files to a dedicated USB thumb drive for backup for the past year. Suddenly, newly created Excel files will not copy. Certain other files that already are on that thumb drive will allow themselves to be overwritten, and the drive shows that it has plenty of room (it's less than half full, and the files are very small in relation to the available space). The Device Manager shows no errors with the drive. The problem is not limited to Excel files. I get an error message "Cannot copy [file name]; the directory or file cannot be created." I inserted a different thumb drive in a different USB port and the problem files copied to it fine. I am puzzled. Can you tell me what might be going on? —Tom Chero
A: You say "the files are very small in relation to the available space"—that's a clue. Thumb drives use a variation on the old FAT (File Allocation Table) file system that was used in MS-DOS. A FAT-formatted drive has a fixed-size root directory. No matter how much space is available, if you fill up the root directory, you can't create any more files. And of course this is more likely to happen if the files are very small because you can pack more of them into the drive. Recopying an existing file is no problem, because it already has a directory entry. If the files have long filenames (any filename over eight characters, or that contains certain characters, such as a space), then they take two or more "slots" in the root directory and hence it gets used up faster.
The solution is simple. Although the root directory's size is fixed, subdirectories can grow to hold as many directory entries as needed. So create a subfolder on your USB drive (you will probably have to move one or more files temporarily off the drive to do this). Now copy any new files into the subfolder. Solved!
