According to Zone Labs, users of PC-cillin (at least 2002/2003) will need to UNinstall their AV before performing the current (4.0) ZA+ upgrade, otherwise it will flash a "PC-cillin Firewall Installed" message, and the installer will exit. Apparently the ZA+ installer id's the registry key used by PCC's firewall--even if it was not installed with the AV component. I have verified this first-hand with Z Labs--unfortunately--and wanted to pass it along as an FYI.