The latest Avast Free works fine with it... at least in Win8. Used it for years also in XI, and now use it with XIV on two systems. Up until Christmas, one of those was an XP Pro 32-bit box. That's now a Win8-64 machine running a fresh install of Avast from scratch, updated to the then current engine at the time of the install. This laptop was also updated last week (v2014.9.0.2011). I play for hours at a time with no problems from Avast on both of them--sometimes 5 hours straight on the weekends.