From Sega Retro
PGen is widely considered the only choice for a Sega Genesis on PS2 emulator. It is even endorsed by Datel and their Action Replay MAX product, and comes bundled with the MAX Media Creator. The original creator of PGen stopped work on the project and released the source code to the public in September 2004. Since then a few members of the gaming community have taken the source and improved its functionality. Currently at version 1.4 the emulator allows booting and loading ROMs from either a USB Stick or the HDD.