Well, you don't connect PC's straight into the internet. Like most things, you sit them behind a competent firewall, and I'm not talking about the one built into your operating system. You can't imagine the incredble age of devices which underpin billion dollar companies, all of which are sitting behind corporate firewalls.
I've got a Win3.1 box, a Win98 box, and an XP box which all have access to the internet -- the difference is, none of the internet has access to those particular boxes. They've been fine for a very long time, and they'll continue to be fine.