Portable Firefox starts with regular Firefox settings
After working right when I first installed it, I invoked Firefox Portable (on Windows 7) and found myself looking at what appeared to be my regular Firefox browser, based on the tabs I had open and other settings. I checked Task Manager, and it was really tbb-firefox.exe that was running. I searched the support site, and based on advice I found there I went into \Tor Browser\FirefoxPortable\Data\settings and renamed the FirefoxPortableSettings.ini file, then reran Firefox Portable, and it worked as expected.