There seem to be lots of recommendations for firewalls such as zonealarm etc., but they do seem to cause the occasional problem. Is the one that comes with XP not really any good? Should I replace it with another, despite possible problems? (Seems to be working ok)
of the WinXP firewall isn't up to much. For one thing it only monitors inbound traffic, and completely ignores anything (like a Trojan) which attempts an outbound access to the internet. The WinXP SP2, shortly to be released, changes all that, and the new firewall is very much improved.
That won't come until June however, and in the meantime I recommend that you instal one of the excellent free firewalls available, like Outpost click here Don't forget to turn off the WinXP firewall before you instal your free download. The new Service pack firewall will be turned on by default when you instal the service pack by the way, so make sure you either turn it off, or uninstall whatever you have been using up to then.