Don’t know whether it’s good or not, but you can’t do that in Clean PC mode. Still, it can be done, you just have to swith to Train with Safe Mode (or even Paranoid Mode, for more control) and create certain rules. Here’s the idea:
What we try to do here is make Defense+ trust every application located on drive C: and not trust applications located somewhere else, right? Well, to do so, you’ll have to define a “trusted” security policy and apply it to everything in “C:*”. In Defense+ / Advanced / Predefined Security Policies add a new one, name it (for example, “Totally Trusted Stuff”), go to Access Rights, set everything you can to Allow. For the “Run an executable” option go to Modify…, and in the list of Allowed applications add an entry comprising all application on drive C: (click Add / Browse…, write “C:*” in the “Add new item” field, press “+”, then “Apply”).
You now have to apply this policy to all the executables on your trusted drive C:. Go to Defense+ / Anvanced /Computer Security Policy, and create a rule. For application Path click Select / Browse…, write “C:*”, press Enter. In “Use a Predefined Policy” select “Totally Trusted Stuff” you just created. Apply. Put this new rule on top of list, and delete everything else (except the groups initially created by Comodo - Windows System Applications, Windows Updater Applications, COMODO Firewall Pro). Apply and switch to Train with Safe Mode.
From now on every application on drive C: (whether Comodo considers them safe or not) will have the access rights of a trusted application, having access to protected files, registry keys, etc., and also being able to launch other applications on drive C: without any alerts. Applications anywhere else will be considered trusted if they are part of Comodo’ safe list, and will trigger alerts otherwise. Applications on drive C: that will try to execute applications on drive D: or anywhere else will trigger alerts too, unless the latter are in Comodo’s Safe list. You could also switch to Paranoid Mode to ignore Comodo’s safe list and have more control on what’s going on outside C:.
Take notice, though, that the whole idea of trusting C: completely is way from perfect. Within the mentioned policy, every new application introduced to drive C: automatically becomes trusted, so you have to be very careful about that.