unable to mount partition

hello.

I'm dual booting windows xp, and ubuntu, booting off the knoppix live cd.

I'm following this guide from a textbook using knoppix to access the shadow file, that stores the root password. So, I start up my command line shell, and fdisk -l doesn't work.. however, because it's my laptop, i know the password, i logged on, and checked that i'm using the sda2 partition for linux (sda1 for windows).

next step is to mount the sda2,

# mount /dev/sda2 mountpoint

(where 'mountpoint' is a empty directory i made)..
I've checked in the /dev/ folder that i do have sda1 - sda15, however
i get these two errors:

modprobe: Can't locate module block-major-8
mount: /dev/sda2 is not a valid block device

I have checked after I rebooted that sda2 is my partition for linux, and it exists in my /dev folder, so I'm confused. I did see a post with a similar question, but nobody responded, and it was really old.

As for the block-major-8 error, a lot of posts were talking about booting from their usb and having issues with that, so that seems very unrelated.

Thanks in advance.