I am trying to mount cdrom by typing the following:

mount -t iso9660 /dev/cdrom /mnt/cdrom

however I get the following message:

mount: the kernel does not recognize /dev/cdrom as a block device (maybe ! ' insmod driver' ?)

It worked ok before. so I am not sure if its something I've done.

Would appreciate some help on this

Sounds like your sym links for /dev/cdrom is not working correctly. First, you need to find out what device your cdrom is, if you only have 1 hard drive and 1 cdrom, then chances are it's /dev/hdc . Otherwise follow this:

Primary Master: /dev/hda (Most hard drives use this)
Primary Slave: /dev/hdb (Mostly used for second hard drives)
Secondary Master: /dev/hdc (Mostly used for cdroms/burners/dvd)
Secondary Slave: /dev/hdd (burners, etc.)

Also, if you have an IDE burner as your cdrom, then you may need to probe the ide-scsi module (modprobe ide-scsi) then try to mount it.

You then should link that to your cdrom device:

ln -s /dev/hdc /dev/cdrom

Then try what you did above to mount it.