Hi Guys.
I totally understand what everyone is saying & you're correct as any security is a fine balance between having all access or no access so reaching a safe middle ground is quite difficult. The machine I'm writing on now is my DAW machine & that is connected to the Internet, however I'm very careful what sites I access & if I'm not sure of certain sites, I don't need to have another physical PC as you can all use Microsoft's Virtual PC which is available for free & you can run a second instance of your OS sandboxed if you're that paranoid.
Other more practical measures you can take which will reduce the threat vectors are to browse the Internet with minimal rights, ie, you're all probably logged on now as Admins? Will lower you're rights when browsing to a minimal user account with hardly no rights, ie, create a User account with no rights so do anything other than browse the web & run your browser with those rights.
Another thing you could do is pay for one of those Sandbox programs & run your browser in that!
One more thing you can do if put a hardware firewall in front of your computer & configure it to only allow access to the sites you require for downloads & software authorisation.
The biggest problem Microsoft machines have & why they get infected with nasty malware is because users do one or several of any of the following things:
1. Don't apply Windows Updates in a Timely Manner
2. Forget to turn on AV programs while online
3. Suft the net with full Admin rights - malware uses the current logged on user's privileges to infect its host
4. Turn off the UAC (User Access Control - requires a machine restart)
Microsoft put that in there for good reason but because it asks you every time you want to perform an admin task & therefore frequently prompts, users get pissed off & foolishly switch it off. Definitely not advisable on a machine which has unrestricted internet access.
I think if you're mindful of the things above & some of the details in my post (link below), you should be okay as that post highlights why AV programs are near useless & why thinking that surfing known trusted sites is okay when in fact there's no guarantee that they've not been compromised:
http://forum.cakewalk.com/FindPost/2898343 Hope that helps.