-The IE skin is pretty good...you might be able to get away with making FF look exactly like IE...
-You need a good AntiVirus. Norton is crap. I don't know about McAfee, but I use Grisoft's AVG Free Edition. It gets the same virus database the commercial version does. It just doesn't have firewall/internet security features.
-Update *everything*. This includes Microsoft updates (
http://update.microsoft.com). Install everything but the driver updates (those tend to break things) and you can forgo Internet Explorer 7 if you want.
-Put your system behind some form of firewall. Even a cheap-y Linksys router will put you behind a Network Address Translation device; this makes it much, much harder to intrude into your system.
-I hope you don't have dial-up...
JBot