[originally posted on the first forum]
Normally I wouldn't make a topic like this. But Sega's been so incompetent in getting us Sonic CD on its own that I fear it never will. To my knowledge, it hasn't been on any compilation thus far, and for all practical purposes the PC version doesn't matter. The beef with the PC version, if you didn't know, is that it won't run with Direct X 9 / Windows XP, because it uses obsolete functionality. That's to be expected when Sega picks such a shoddy company as Expert to do its ports (and if the buzz on SADX PC is any indication, since the disappearance of Expert they've taken up the burden of making shoddy ports themselves).
So here is exactly what you need to do to get it working.
1) Get
Gens, a Genesis/SegaCD/32X emulator. Make a directory somewhere on your PC and unzip it there.
2) Head over to the ISOs page of
Sonic Stuff and download the BIOSes and the American or Japanese version of Sonic CD (they're all around 25MB zipped, so get ready to wait if you're on dialup). An ISO is kinda like a ROM, except it's a CD image instead of a cart. None of them have music. Unzip them to the same directory you put Gens in. If you don't care about music, you can skip the next two steps.
3) For the Japanese soundtrack (which is almost universally preferred over the American, though I like both), head over to
this place; you need a GameSpy ID to download anything. If you don't have a GameSpy ID, try
Sonic Stadium; they seem to be down now, but hopefully it'll be up by the time you try it. Prolly hackers again. All the music should be in the same directory as everything else. If anybody wants the American soundtrack I can rip it from my dysfunctional PC copy of Sonic CD, since I can't find it online.
4) Now we have to rename all the music files so Gens recognizes that they go with Sonic CD. They should be named as "[game name] [track].mp3", where [game name] is the name of the .iso. Time Warp (which you don't have, but isn't used in the game anyway) is Track 02, and numbering goes up from there. You have to number them 03, 04, etc - if you just use one digit, it won't work. So if you downloaded the American ISO, Palmtree Panic Present should become "scd_usa 03.mp3".
Edit: Here's the track listing, stolen from Sonic Cult.
2. - unused track -
3. Palmtree Panic Present
4. Palmtree Panic "G" mix
5. Palmtree Panic "B" mix
6. Collision Chaos
7. Collision Chaos "G" mix
8. Collision Chaos "B" mix
9. Tidal Tempest
10. Tidal Tempest "G" mix
11. Tidal Tempest "B" mix
12. Quartz Quadrant
13. Quartz Quadrant "G" mix
14. Quartz Quadrant "B" mix
15. Wacky Workbench
16. Wacky Workbench "G" mix
17. Wacky Workbench "B" mix
18. Stardust Speedway
19. Stardust Speedway "G" mix
20. Stardust Speedway "B" mix
21. Metallic Madness
22. Metallic Madness "G" mix
23. Metallic Madness "B" mix
24. Boss!!
25. Final Fever
26. Title
27. - unused track -
28. Zone Clear
29. Speed Up!!
30. Invincible!!
31. Game Over
32. Special Stage
33. Little Planet
34. Opening
35. Ending
5) Almost there! Open up Gens. If you try to load Sonic CD, you'll notice it complains about the BIOS files. What to do? Head over to Option -> Bios/Misc Files and you'll see a dialog for Sega CD bioses, with different countries. Hit Change and find the BIOSes you downloaded; you only need it for the country version you downloaded, but it doesn't hurt to set them all. The difference is that only the American BIOS calls it Sega CD instead of Mega CD and the European version is 50fps instead of 60 (which is why I said to download American or Japanese earlier). You may also want to hit Option -> Joypads to see what the input settings are as well.
6) Now if you try to load Sonic CD, it seems to work, but hit Start and it'll complain about RAM. Reboot (Tab) and hit A instead, and it'll take you to the CD player. Find Option and hit A again; it'll show you statistics and then take you to memory controls. Format the RAM and restart again. The game now should be fully working. Have fun! :)