Sonic & Knuckles Collection is a compilation for Microsoft Windows based PCs, released in 1997. Games included are Sonic the Hedgehog 3, Sonic & Knuckles, Sonic 3 & Knuckles, and Blue Sphere (listed as 'Special Stage Mode').
Most of the original music is emulated, with the user able to choose between MIDI and FM formats. Furthermore, some of Sonic 3's music tracks, including those of Carnival Night Zone, Ice Cap Zone, Launch Base Zone, Knuckles' theme, the Competition menu, and the credits music, were replaced with original compositions. One possible explanation for this is that the tracks featured sampled sound effects not supported by the MIDI standard, and some sound cards during this time were not capable of playing these alongside the standard MIDI instruments. Another potential explanation is that the original tracks may have been composed by Michael Jackson, and were removed due to legal reasons that arose since their original release. Aside from this musical difference, the game plays virtually identically to its original incarnations.
In the US and in Europe, 'Sonic the Screen Saver' was included in the compilation. This disc allowed users to customize Windows with Sonic themes, wallpapers, icons, and play music from Sonic 1, 2, 3, S&K and the Japanese version of Sonic CD. In Japan, Sonic the Screen Saver was sold separately.

Sonic CD is an old dos game, published in 1996 by SEGA Entertainment. Main genre of this old game is action. We gave this game stunning rating of 89 and you can download it for free right here. In the '90s raged the big console war in the gaming industry, and Nintendo was winning it, thanks to Mario. SEGA has therefore come with its own gaming legend: Sonic the Hedgehog. In 1996, this game was also ported to Windows OS asnd so was Sonic CD created (many fans refer to this version as the greatest one of the series). Sonic the Hedgehog along with his girlfriend Amy Rose travel to Never Lake, where they reveal the insidious plan of Sonic's archer enemy Dr. enemy. Eggman to manipulate the time. Dr. Eggman created an evil Sonic twin - Metal Sonic, who kidnaps Amy Rose, and your task is now not only to save Amy, but also to stop Dr. Eggman. Gameplay is that what you would expect from Sonic's game: you run fast and I mean FAST, collect rings, jump on the robots to destroy them, collect powerups - just have fun the Sonic way.