In case your Computer is connected to the internet for sending and receiving e-mail or browsing the net, you need Norton Activation. This applies whether there is a dialup connection or a high-speed connection like cable or DSL.
The fact that you will be connected to a network that is public along with millions of others means that the PC is exposed. It is open to receiving a large number of small software applications which are created specifically use, interrupt, or to either damage your pc.
Protecting your pc against malicious intruders
If you get a file from another source on the internet, there's an opportunity that file will be "infected" using a virus, or will include an attached touch of adware or spyware. That applies to receiving email messages, and viewing web pages. It also applies to downloading video files, sound, and picture.
Email attachments are especially notorious for harboring malware and viruses. You get a message that comes with an attachment beckoning you to double click on it. When you are doing so, it installs a small application which lives somewhere deep in your Personal Computer, prepared to do whatever it continues to be programmed to do -- whether that's spying and reporting on your own pc customs, hijacking your home page and redirecting you to another site, or popping up aggravating advertising for gambling or pornography sites.
Viruses go well beyond that. They can be deliberately made to run software that damage significant operating system files, and generally possess some means of using your email program to send the message that was infected to hundreds of others in your contact list. That's the reason they can be called "viruses" -- because they are able to spread like wildfire to thousands and even millions of computers that have not Norton Activation installed.