[问题]ubuntu 7.10 DVD file can NOT be mount as iso9660 type.

[sausame]

I download a DVD file of ubuntu named: ubuntu-7.10-dvd-i386.iso, and I want to mount it as a device:

$: sudo mount -o loop -t iso9660 /media/d/Software/ubuntu-7.10-dvd-i386.iso /media/cdrom0/

But it is failed. I use "dmesg | tail" command to know what happened, it prompts that:

[ 3068.301318] Unable to identify CD-ROM format.

The file is full, and checked with MD5 code. I have burn it to a DVD ROM, and use it to install my Ubuntu system.

What's the reason? Could anyone tell me? Thank you very much.