This is just a snippet of information i have found and solved about ESXi 3 and 4 with regards to mapping a USB device. ESXi can use ti as a USB device ONLY if the linux kernal supprots or realises its a USB CDrom. More often that not this wont work and you wont be able to choose CD/DVDrom, what this normally means is that the device has been detected but its been mounted as a scsi HDD. So instead of adding a CDROM to the guest operating system add a HDD to the guest Operating system and hopefully you should be able to choose the CDROM / DVDROM as a HDD instead. Works just the same just doesnt appear as a cdrom. Apparently you can go into the troubleshooting mode on the ESXi command prompt and re mount/point the sda or sdb (or whatever the cdrom has mounted as) to \mnt\cdrom\ although i haven’t tried that.