Well, first thing first - what do you mean by "login root"?
2. The modprobe command is /sbin/modprobe you need to be root to do so, on how to become root read further
3. As for mounting permissions - you need to edit /etc/fstab file to include user
option like this
/dev/cdrom /mnt/cdrom iso9660 user,noauto,ro 0 0
Now the root login thing, as a good security practice never login to your system as root but use substitute user command (/bin/su) to gain root's priveleges, oopen up a Konsole/Gnome Terminal/Xterm or other terminal emulation software available on your system, and issue
[you@host ~]$ /bin/su
[you@host ~]$ Password:
type the root password you won't see anything on the screen (echo is turned off once again as a security measure)
now you can issue commands as root, for instance to get /sbin/modprobe type
[root@host ~]# /sbin/modprobe ac97
and to edit /etc/fstab use something simple, most probably you have gedit so issue
[root@host ~]# gedit /etc/fstab
do the changes and save the file and you done.
Last is regarding netzero it won't work as it is designed to work with Internet Exploiter - dumbest ISP I've ever known, you can try aol with pengaol - refer to this tutorial
but it is not guaranteed it will ever work, so I guess you should research other ISP - google around.