Synopsis:

        sys_diskfree(driveID)

Arguments:

        driveID     -  The ID of the drive (0=A:, 1=B: etc)

Description:   Returns the amount of disk space available on the specified driveID where driveID=0 represents A:, driveID=1 represents B: etc

Return Value:

Returns the amount of space left on the specified disk drive or a negative error value if an invalid disk is specified.