I agree with The3ntropy on this...2 firewalls can conflict with eachother, and from what I've experienced with Norton Internet Security 2002 (my only firewall besides windows xp's built in firewall which I don't use) is that it slows my internet connection down quite a bit. playing online games is tough, so I have to turn it off when I play games. so my guess would be that if you have 2 firewalls packets must go through, it will slow your connection down twice as much as 1 firewall.

just make sure you have one firewall that is properly configured, and you should be fine. but if you're trying to secure a server or network (which I don't think you are), you would want to use multiple firewalls (on different computers/routers; I won't go into a network topology tutorial so I won't be able to explain it in full). For regular home use, you should be fine with a single properly-configured firewall.

-Nitro-