I'm just upgrading to XP 64 bit in the hope it will cure my OOM's in FS9

I've been using Zone alarm free for the last 100 years on my old 32 bit systems.. I can't find a version of Zone Alarm that will operate on XP 64 Bit.. Is the standard windows firewall sufficient or is there a decent firewall out there that I should be using... Obviously I would prefer a free one but I don't have a problem paying for a payware one providing it's not too expensive and it's easy to use..

Cheers

Steve