I have a Nec DVD RW ND-3520. Until recently, it worked with no problems in both Slackware 10.2 and Windows XP. However, today I had a scratched cd causing some trouble while trying to umount it, so i did umount -f. Since then, no cd-rom or audio cd can be read in neither linux nor windows. Interestingly enough, dvds are read with no problem.

Any idea how I can fix this problem? Is it really possible that umount -f screwed my dvd writer?

Are you trying to mount an audio CD? Music CD's lack a valid file system, so the mount command won't work.

Either way, the umount command didn't affect your drive. My guess is that perhaps the drive is still mounted, or at least the system thinks it is. The cheater way to solve it would be to just reboot.

I though I made it clear that I rebooted several times.
I know that audio cds can't be mounted, I wasn't trying to mount them. I tried to play them with a cd playing software, but nothing happened. And when I try to mount regular cd-roms, I get error message "no media found" (or something like that). AND Windows XP can't read cds, too. BUT dvds can be read/mounted normally, in both Windows and Linux.

I have no idea what I did to screw up the dvd drive...
I guess there's nothing I can do now, but take to the repair store.
If someone has any idea, please do tell.

Thanks.