Although the device per se (/dev/sr0) is seen by, for instance k3b,
when I click it it says no disk found(there is a blank CD in it alright)
Any tips what to check?

So what are you trying to accomplish? You can not mount a blank CD.

I want to write some directories to that blank CD and when it comes to the burning step it says disk not found
Also, even when I put a non-blank data CD in the CD-R and click it, it still says disk not found

Are you saying I need to do
mount /dev/sr0

? Then why does k3b see the device if it's not already mounted?

Devices and filesystems are not the same thing. You mount the filesystem not the device. A blank CD does not contain a filesystem.

What distribution and kernel are you running?

Distro is Slack 9.1 (2.4.22)
I get a disk not found also for a non-blank CD

I'm not too familar with Slack. However, your CDRW should be configured for SCSI simulation and the device ID is usually /dev/scd0.

What does /etc/fstab say is the device ID for the drive? If it is something like /dev/cdrom then also post the output of
ls -l /dev/cdrom

You may also try running the k3b-setup program as root. It will modify the fstab entries if needed. If you use lilo, post the append= line for the /etc/lilo.conf stanza you boot up to.

Exactly. You can write to a CD without mounting it. In fact, this is what you should do. You don't have to mount a device to use it. For example, when you write a floppy image to a floppy, you write directly to /dev/fd0, no mounting required. Same to CDs.

Not too sure about the CD-R thing, I just thought I'd throw in my $0.02

here is fstab:
~$ cat /etc/fstab
/dev/hdb3 / reiserfs defaults 1 1
/dev/hdb4 /home reiserfs defaults 1 2
/dev/hdb1 /boot ext2 defaults 1 2
#/dev/cdrom /mnt/cdrom iso9660 noauto,user,ro 0 0
/dev/hdc /mnt/cdrom iso9660 noauto,user,ro 0 0
#/dev/fd0 /mnt/floppy auto noauto,owner 0 0
/dev/fd0 /floppy auto noauto,user 0 0
##### NEW to add cdrw
/dev/cdrw /mnt/sr0 auto ro,noauto,user,exec 0 0
#/dev/scd0 /dev/cdrw auto ro,noauto,user,exec 0 0
##### end of change
devpts /dev/pts devpts gid=5,mode=620 0 0
proc /proc proc defaults 0 0

ls -l /dev/cdrw
total 1
lrwxrwxrwx 1 root root 8 Aug 1 00:28 sr0 -> /dev/sr0

$ ls -l /dev/sr0
brwxrwxrwx 1 root disk 11, 0 Apr 13 1999 /dev/sr0


Finally LILO:
$ cat /etc/lilo.conf
# LILO configuration file
# generated by 'liloconfig'
#
# Start LILO global section
append="hdd=ide-scsi acpi=off"
boot = /dev/hda
message = /boot/boot_message.txt
prompt
timeout = 1200
# Override dangerous defaults that rewrite the partition table:
change-rules
reset
# VESA framebuffer console @ 1024x768x256
vga = 773

# End LILO global section

# Linux bootable partition config begins
image = /boot/vmlinuz
#image=/boot/vmlinuz-2.4.22
root = /dev/hdb3
label = Linux2.4.22
read-only
# Linux bootable partition config ends

# Linux 2.2
image=/boot/vmlinuz
root=/dev/hda2
label=Linux2.2
read-only
#2.2 bootable partition ends


Does this look ok?

No.

Look here:
Should be rw, not ro.

Just to make sure, run and look at the output or post it here.

You made sure that /dev/sr0 is linked to /dev/hdd I presume?