A control apparatus is provided for controlling a drive apparatus to access a rewritable information recording medium using a first file system. The control apparatus includes a first determination means for determining whether or not a matter which is not permitted in a second file system exists on the information recording medium; and a second determination means for determining that there is a possibility that the valid data in the first file system is recorded in a first file system space when it is determined that a matter which is not permitted in the second file system exists on the information recording medium.