FYI:
The download links above are for a "Special Edition" ISO I made, which replaces the game's American soundtrack with the original Japanese soundtrack. The PC version was released in all territories with the American music, even in Japan (which is why I made the Special Japanese ISO).
Sonic CD (Original Unaltered ISO)
Download(s):
For the Special Japanese ISO, you need the K-Lite Codec Pack to watch the cinematics in-game. You shouldn't need it for the original ISO though.
Link:
http://www.free-codecs.com/k_lite_co...k_download.htm