Having spent the best part of a morning and 700 MB of expansive bandwidth (downloading new installers that didn't work in respect of COMODO.) trying to sort out a problem involving interactions between Avast and COMODO, I'm still puzzled as to why products from different vendors apparently interact in a manner that causes problems.
The problems started with a recent update to COMODO, which was performed via it's internal update process. On the subsequent re-boot, the system locked up such that it wasn't even possible to get either of the COMODO or AVAST user interface (or even the standard Windows Task Manager to load.)
In the end I had to reboot into "Safe Mode" , Repair AVAST which was not easy to do given that the portion of AVAST responsible apparently makes assumptions as to the display size, which are inappropriate running in absolute basic VGA (as in Safe Mode).
Given past advice given both here and elsewhere, I then de-installed both COMODO and AVAST. I then reinstalled AVAST from the offline installer someone else linked to in a previous thread on this topic. Avast duly reinstalled and ran with out issue ( COMODO being absent). I then assuming that the problem lay with COMODO, re-downloaded the installer directly from COMODO's website. On the three subsequent attempts to get it to install, COMODO's installer failed with cryptic error codes on EVERY single occasion. This I find unacceptable, and have filed a ticket with COMODO expressing my dissapointment (given that they previously claimed to have resolved this particular issue.)
As I don't like running without a firewall, I downloaded the XP version of Zone Alarm Free Firewall instead, this installed but generated various "No Disk" exception messages during installation. (sigh)
In respect of the issue with Zone Alarm, I went to it's forum to try and get an answer only for Firefoz and Zone alarm to apparently stop the posting, complaining about a badly configured site. (sigh)
I will of course be running a scan in AVAST to make REALLY sure there isn't something on a local disc that definitely shouldn't be there, but I'd also appreciate someone from AVAST make some strongly worderd enquires in the direction of both Comodo and Check Point (in respect of Zone Alarm) with a view to determining precisely how their programs or installers might be doing that conflicts with what AVAST is actually or thinks it's doing.
At least AVAST was kind enough to warn that portions of Comodo Internet Security may be incompatible. The same cannot be said of COMODO's installer, or that of Zone Alarm.
Perhaps someone from AVAST would also be able to help determine if the above mentioned issues are indeed down to a glitched (but hopefully not infected) installer, or are indicative of a more serious issue requiring more specialist expertise to determine. (The thought was that there was some kind of configuration residue left behind that was causing COMODO or AVAST to hiccup.).
The COMODO firewall installer was from here :
https://personalfirewall.comodo.com/
