I use comodo internet security, and it's a bit annoying at first, but the firewall, antivirus and the sandbox features make it a far superior product than most retail internet security products. I would recommend setting everything to training mode for the first week or so, until notifications stop popping up. If you also install the retail version of Malwarebytes and enable the realtime scanning, nearly everything you throw at it is caught. I've been using both in xp and in windows 7 machines for several months and have had no problems with either, although prior versions had a tendency to attack the synaptics touchpad app in some laptops. If you have any problems with it, the comodo forums are quick to give good advice..
a bit of advice:
don't mess with custom or advanced settings until you know what you're doing and keep it up to date.