my gf is one of those ppl with the horrible habbit of downloading anything and everything the internet tells her she needs how can i use FF to better protect her from the various virus she downloads on a regular basise

as i write this i have just restored my gf's computer back to default factory setings and cleaned the HD she has a horrible habbit of downloading anything and everything something tells her to download it her most recent actions caused her to dl a virus along with a prog called "flv tube" ive never heard of it but in less then 5 mins on google i found it to be common with viruses how can i use FF to prevent and or stop her from downloading all this crap so im not always having to fix it for her