I installed CPF to test it, using the default configuration, but with XP Firewall active. After rebooting I did not have access to the network. Even giving an application (Firebird) complete access or setting a global “Allow all” did not open the network access. Also disabeling XP Firewall did not change anything.
If you have a network/router you must go to security/tasks and “define a new trusted network”.
There is no point to have XP firewall at the same time as Comodo firewall. You don’t get better protected, and you only increase the risk for conflicts. And if you also have a router, even the router have an inbound firewall built in to it.
If it still doesn’t work after you have made a trusted zone, and if you have the default rules after choosing “auto” at install, you might have to reinstall it. Just turn off XP firewall before you install.