Hello wildflowerpam, '''yes''' you need an antivirus protection not only with firefox but with every browser you use. Web browsers do not have antivirus protection. You can seek, in the next link for extensions, who help also your safety in browsing like, [https://addons.mozilla.org/en-US/firefox/addon/adblock-plus/?src=hp-dl-mostpopular Adblock Plus], and [https://addons.mozilla.org/en-US/firefox/addon/noscript/?src=hp-dl-mostpopular NoScript Security Suite]. https://addons.mozilla.org/en-us/firefox/ i think the programs you mention it is compatible with your win xp (of course it is compatible with firefox). thank you