Play knuckles games on your Computer! yes it's right you truly can BUT you need an emulator AND you have to delete roms of your system in less then 24 hours. Enjoy! :)
Emulators:
visualboyadvance
Gens Genesis/megadrive emulator
Roms:
Sonic2 & Knuckles
Sonic3 & knuckles
Sonic & Knuckles