Under Vista / 7, depending on how the user accounts are set up, if you install the game to the default Program Files path, Windows can create separate savegame folders for each user, and then map that folder to the game's savegame folder (so it will just see the saves for the relevant user).
The 5 'bd_act#_start' folders are used by the game for initial data for each act.


Rather than the '..\Beyond Divinity\savegames' folder, check:

C:\Users\ %account name% \AppData\Local\VirtualStore\Program Files\Larian Studios\Beyond Divinity\savegames


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