You can set PANDA_PRC_PATH to the directory that contains the Config.prc file. But this shouldn’t be necessary, because Panda should find it automatically based on the location that libp3dtool.dll was found. Is it possible that you have multiple copies of libp3dtool.dll, and it’s loading the wrong one? Or that you have installed libp3dtool.dll into a new, nonstandard location?