Sonic & Knuckles Collection is a Sonic the Hedgehog compilation game for Microsoft Windows-based PCs. The ports have all of the music emulated in MIDI format. Some music (Carnival Night Zone, IceCap Zone, Launch Base Zone, Knuckles' theme, the Sonic 3 Credits theme, the sub-boss music from Sonic 3, and the Competition main menu) was replaced with original music. One possible explanation for this is that the pieces of music from the Genesis version used sound effects not contained within the general MIDI standard, and many sound cards at the time of release did not have the capability to play additional samples along with the MIDI. Another explanation for the replacement is that the songs were replaced due to legal reasons, because connections could be made between similar songs by Michael Jackson. Other than that, the gameplay is identical to their Mega Drive / Genesis counterparts.
This game is virtually impossible to play in windowed mode on any system with a CPU faster than 350 MHz, because the game does not have proper speed-limiting routines in this mode. However, the timings used by the game are based on the monitor's refresh rate. Switching the game to fullscreen mode lets the game play properly, no matter what your system speed is. In windowed mode, the game can be played at the correct speed whenever the screen refresh rate is at 60Hz. Sega has also provided a patch to fix this problem without reducing the refresh rate.