If everything worked well until you rebuilt the kernel then it suggests you missed out SCSI CD-ROM support or something else it depends on, or some of your modules to give you the support are not loading. Check your kernel config again... once the kernel is sorted out you will still need to recreate the special device that your friend told you to delete - bad move! The /dev/cdrom symlink is normally there so that you don't have to remember which device your CD-ROM is, and provide a little abstraction - some people argue that its a bad idea to use symlinks, but I've never had problems. To create the special file use the following in the /dev/ directory
I can't say I've ever needed to use mknod but according to the man page the above code should work.