Before you install SP 2, why not, for safety sake run through all the steps again in PP's Sticky
Do this just to be sure that the system is clean.
The key to an uneventful install of SP2 is to do it on a machine you are certain is s completely free of viruses, worms, and spyware.
As another precaution, before you install SP2, you need to disable antivirus software you're using and close any open programs. This is always a good idea before installing new software, but it's especially important when you're installing a service pack. And for SP2, it's important that you disable any antivirus software especially. Some antivirus software can interfere with the SP2 installation. To disable the software, follow instructions from the antivirus software provider that you use. Check the software provider's Web site for exact steps.
You said you uninstalled the EZVirus Suite but don't mention what anti-virus program you have installed to take it's place. Be sure to visit the website of this new anti-virus program to find out how to TOTALLY disable it prior to installing the SP2
Now, about the Windows Firewall;
Windows Firewall blocks only incoming stuff whereas third-party firewalls (such as Zonealarm and Sygate) block both incoming and outgoing stuff. This means that were you to inadvertently allow a trojan to be installed, WF would not prevent it from calling home with whatever information it had managed to harvest from your computer (passwords, monitored keystrokes, etc, etc). So, in theory, a third-party utility will offer a greater level of security than WF. However
... simply adopting safe surfing practices (not downloading applications from warez sites or via file-sharing utilities, not installing no-cost applications from little-known developers, etc, etc, etc) and running a good antivirus utility should be sufficient to prevent any trojans or other unwanted items from finding their way onto your computer and so a bi-directional firewall is, in MY Opinion, of less importance than many people seem to think.
There is, however, no "one size fits all" answer here. Should you use your computer for online banking/shopping and should it be shared with file-sharing children, then it might not be a bad idea to install a third-party firewall. on the other hand, if you trust the other users to surf sensibly, then Windows Firewall is probably perfectly sufficient for your needs. I, myself, use the Windows Firewall and have had no problems whatsoever. But I also follow the practices I stated above too. I also practice good maintenance on the computer...at the very least weekly...I run AdAwareSE, Spybot S & D, I also have SpywareBlaster installed, updated and enabled and I run my anti-virus program weekly, at a minimum. I keep my temp files and internet temp files emptied and I have had no problems at all.
It all is really up to you. Each person has to make his own choice. A word of advice though, since you did have problems with the Zone Alarm portion of EZTrust if you do choose to go with another firewall I would choose one of the others that are listed in this thread
PROTECT YOURSELF FROM MALWARE: Tools & Tips
Good Luck and keep us posted!
Judy