If you are concerned that your friend's CD is modified in some way, then buy or burn your own CD. It's cheap and perfectly legal.

If this sort of thing is happening:

Code:
$ touch /root/whatever
touch: cannot touch `/root/whatever': Permission denied
Then you need to first become root by using the su command:

Code:
$ su
# touch /root/whatever
# ls -l /root/whatever
-rw-r--r--    1 root     root            0 Aug 19 14:30 /root/whatever
Finally, if you have something to add to one of your previous posts then use the Edit button. This reduces clutter.