PCGamingWiki[www.pcgamingwiki.com] is the best source for this, and it doesn't disappoint here. Just note to use the Steam option, not the WIndows one:

<Steam-folder>\userdata\<user-id>\1018010\remote\

Where your Steam folder is the install folder for Steam (default in Windows 10 is %ProgramFiles(x86)%\Steam\), and the user ID is a numerical ID assigned to your Steam account (you are, after all, just a number to them).

To get the value of your own steam ID:

Open Steam, and click your profile name near the top right corner of the screen.
Select "Account Details" from the drop-down menu.
Your steamID is directly under your account name (aka username)


So you can open %ProgramFiles(x86)%\Steam\userdata\ in Windows explorer, select your Steam ID, and then go to the folder 1018010, which is the SteamID for the Castlevania Anniversary Collection. Note that you need to have played the game once for the folder to exist.

From there, the "remote" folder is where all of the save games are stored. data_008_0000.bin is the save files stored in all games from the in-game save feature for the Advance collection, and I think here it's where it tracks which games you've played (once I copied it over while I was testing, the achievement for playing each game popped immediately), while the rest of the files (data_012_0001.bin, data_014_0001.bin, etc) are save states made using the Anniversary collection's menu.

With this you can back-up your save files in another folder, or add new save files, like what I have shared in the next section.

Note that there's a second "savedata" folder, saved in the "Users" folder in Windows:

C:\Users\[Your Username]\AppData\Roaming\Castlevania Anniversary Collection\savedata\

These aren't unique to different Steam accounts but seem to include configuration data. I'm not sure if you need those for the save states (I've confirmed that they aren't the save states), and my testing was inconclusive (once it worked without them and once it didn't), so it doesn't hurt to update or back-up that folder, too.

Here are save files made right before getting every achievement in the game.[drive.google.com]

What you need to do is copy the desired files into the "remote" folder (and the "savefile" folder) as described in the last section. In some games, you need to do this with the game open or the Steam Cloud save back-up feature turned off, but I didn't have any trouble with this game. But if you are having trouble, try turning off the steam cloud back-ups in the game's properties (right-click on the game in your steam library, go to Properties.

Copy the files in your folder, open the desired game, and load the save state. The other error that may occur, is that you may need to make save states first and then copy over the files; I had some issues when trying this on the other Steam account in the family.

Once in the game, the achievements should unlock. In a few of the games you have to make the last motion before beating the game - collecting the orb, typically, but it should unlock after it counts the final score.

For Castlevania III: Dracula's Curse and Castlevania Bloodlines, there are multiple endings and thus multiple achievements. Just pick the ending out of the relevant folder and copy it into the main "remote" folder and it should work. You don't need to exit the game; just copy over the save file and hit load again.

Feel free to use these as you wish, but I recommend trying to play the games and have fun to get the achievements. but if you missed a boss achievement or don't feel like playing Bloodlines or Dracula's Curse multiple times, these are here for you!

Hopefully this helps you in either backing up your save files or getting that one last nagging achievement! The files should all unlock an achievement, I tested them on another Steam account in my family.

Let me know if you need further explanation or have any thoughts in the comments.