I use Chrome (moved from Firefox as it became more flaky and kept slowing down as a "normal" event). I have added AD BLOCK Plus TO Chrome and also have Avira Browser Safety installed. I use Windows Defender and occasionally use a free version of malwarebytes and their rootkit version and haven't had any issues in over a year since I went that route.
On XP, I suggest using AVG Free antivirus and occasionally run Malwarebytes Free.
http://free.avg.com/free-antivirus-download
https://www.malwarebytes.org/mwb-download/