Use one PC/Mac for WoW and once PC/Mac for browsing/downloading, and you'll be fine. At home I have a Linux PC to browse with and a Win2k PC to play at, never had a virus on the WoW comp for 3 years or so. Well, nothing that my anti-virus and firewall has picked up anyways....

And yea, I know there are addons for Firefox that does the thing, but it's not the same. <3 Opera