You need an ISP to connect to the internet, but you don't need to install any software from the ISP. All those disks normally do is automate the process of setting up the connection - which you can do manually yourself.
Beyond that, they often install a branded copy of Internet Explorer, and set the home page to be that of the ISP, none of which you need.
All you actually need are:
A working modem or router
a user name and password
The address of the SMTP and POP3 mail servers of the ISP, and possibly a separate password for collecting your e-mail (as opposed to the one for connecting to the internet).