On entry, a logical
drive number (1=A, 2=B, and so forth) is specified. On return, if the device
has more than one logical drive letter assigned to it, a drive number corresponding
to the last drive letter that was used to reference the device is returned.
For example, if the entry drive number was 1 (where 1=A) and the returned
drive number was 2 (where 2=B), this drive was last referenced as the B:
drive. If only one drive letter (logical drive) is assigned to the
device, a zero is returned.
Note: This function works as long as the file handle is valid. The
file handle can be set to anything other than zero.