Code:
/dev/acd0 /cdrom cd9660 ro,noauto 0 0
/dev/acd1 /cdrom cd9660 ro,noauto 0 0
Don't give 2 devices the same mount point.
Also, DVD's typically use the UDF file system.. not ISO9660. (s/cd9660/udf)
fstab(5) aliases get complicated with mount points that may use different file systems.. consider mounting disks manually.
If that's not an option, you could re-purpose each of the available drives.. i.e: /mnt/cdrom and /mnt/dvdrom..
Code:
/dev/acd0 /mnt/cdrom cd9660 ro,noauto 0 0
/dev/acd1 /mnt/dvdrom udf ro,noauto 0 0
So you could inset a DVD into the second drive.. and then type "mount /mnt/dvdrom".
The choice is yours.