RE: Need firewall protection,

OK, it is starting to sink in. <g>  NATing routers block/deflect all
"uninvited" guests.

I am going to ask one more question relating to this.  Couldn't a router be
fooled, "spoofed" if you will, by an "uninvited" guest on the outside
sending something to the router so that it believes it is a result of
something initiated on my PC?

Or are there just too many variables for it to happen?

Let me suppose the following high-level pseudo scenario:

A potential "uninvited" guest is monitoring traffic between my firewall and
the website I am visiting.  The website sends something back, which the
firewall accepts based on the information being sent back.  What's to say
that that information couldn't be intercepted to capture the "keys" that the
router needs to let it in, and then use those "keys" to send something to
the router that the website didn't send?  How does the router/firewall
assure that the information it receives is coming from a source that the PC
initiated?

Thanks again for all the replies!  I have learned an enormous amount from
you guys, and I really appreciate it!

- Dan