@REMOVABLE[d:]: Returns 1 if the specified drive is removable (e.g. floppy disk, removable hard disk, USB storage device, etc.), 0 otherwise. The drive letter must be followed by a colon.
If the argument is a partial filename without a drive, @REMOVABLE will expand the filename to get the drive.
Examples:
echo %@removable[e:]
1
echo %@removable[%_disk]
0