I have just installed "Zone alarm" as recommended on here many times. It does appear to slow the pc down since the download. I realize it is "learning" about this pc and should speed up in time (am I right?) but I wondered if I need to remove or disable Windows firewall to prevent confliction between the two.
Thanks.

You cannot have two firewalls running at the same time on a PC, they will conflict with each other, disable Windows Firewall and see if your PC speeds up.

I've used Zone Alarm myself in the past, and don't care much for it, it conflicted with other programs on me, but that's just my opinion. Lets us know how you get on. :)

Zone Alarm when first installed, is very noisy, alerting you to it seems like everything. If you knoe\w the program is safe, when the box comes up, click remember this decision or something like that, then click Yes or OK. I've been usiong it for about 9 years now and swear by it. If it does slowthe computer a tad bit, that's okay with me, rather be safe than sorry.

Zone alarm will slow your computer down...a lot....notice the 10 or so seconds when you see your wallpaper but the pc's not doing anything, that'll happen for the rest of zonealarm's life.. You will have to disable windows firewall if you've got zone alarm (and I use this word lightly cause it's more of a crawl) "running" as their rules can conflict but zonealarm should have shut it off during install. Although some other regular users recommend zonealarm and "swear by it", it's possibly the most slowest program ever to be developed and works on the principle of waiting for hackers to get bored of your pc's dreadfully slow responce time. I would be happy with the following on any pc:
Eset Smart Security (Proven the lightest full security suite)
Norton 2009 internet security (2009 Only, every older edition is very very slow)

Second to these would be
Kaspersky
Mix of comodo and avast

Then
Zone Alarm
MyDoom worm

Hope that helps

If you have XP and 1-2 gigs of ram you should not see any speed issues with ZoneAlarm... I have a computer with 1 gig and a laptop with 3 gigs, neither have any issues with slowness... I assume you must either be running Vista or have less than a gig of ram.

I highly recommend you stick with ZoneAlarm and/or use Comodo... The latter being more secure in a way but also is based on rules and not just applications... Comodo also has a far better virus scanner with it then ZA does.

Here are my suggestions:

1. Disable windows firewall, it is garbage... It should only be used if absolutely no other firewall is on your computer... But I would not recommend it.
2. Click ALT + CTRL + DELETE and check cpu usage... If it is a high percentage and you have more than a gig of ram you should try and figure out what program/s are hogging the ram. You could try starting the computer in diagnostic mode by going to START >> RUN >> type MSCONFIG and click enter... Then check DIAGNOSTIC SETUP click ok and restart... Then try running ZoneAlarm and see if the computer is still slow. If it isn't then you have a app hogging your resources.
3. If you have less than 1 gig of ram upgrade to at least 1-2 gigs... 3 for Vista.