When you start F@H the first time, it asks you if you want to adjust the advanced configuration as well. Go for yes. The important thing about two F@H instances on one PC with two cores is that you give each a different ID. IIRC, the very last question of the advanced options is the Machine ID. Make sure you give different numbers to each F@H client. That should solve the problem. Oh, and of course, you need to have two copies of the F@H console in two different folders, to do this. You can't start the same console twice. 🙂