More info:  
http://www.gog.com/en/gamecard/the_witcher_2/  
http://store.steampowered.com/app/20920/ 

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What's New in the Enhanced Edition: 

Additional hours of gameplay: New major adventures set in previously unseen locations, expanding the story and introducing new characters, mysteries and monsters. 

New Game Introduction and Cinematics: All new animations and cut scenes, including a new, three and a half minute pre-rendered cinematic depicting the assassination of King Demavend of Aedirn. BAFTA Award winner and Academy Award nominee Tomasz Baginski brings this key historical event to life, setting the stage for the story told in The Witcher 2. 

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The player is Geralt of Rivia, a professional monster slayer, a witcher. Entangled in the political turmoil that engulfed Temeria, Geralt helped quell the rebellion of the Order of the Flaming Rose. Soon after, he saved King Foltest?s life when the monarch was attacked by a witcher-like assassin. He continues to protect the king, serving as his bodyguard as Foltest strives to bring peace to his kingdom. The Order?s last bastions have yielded to the royal army, yet one more task remains - the Baroness La Valette announced her secession from the realm, and her fortress must be taken. A month after the attempted assassination, Foltest?s armies stand at the gates of La Valette Castle, preparing for a final assault. Still at Foltest?s side, Geralt is among them, unable to begin his personal quest to discover the mysterious assassin?s origin and identity? 

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Version: 3.0.1.17 
From GOG.com 
-- DRM Free 

SFV checks of all the files are inside the "misc" folder. 
The GOG.com extras are inside the "extras" folder. 
The game installation files are in the "setup" folder. 

Min requirements: 

OS: Windows XP/Vista/7 
Processor: Intel 2.2 GHz Dual-Core or AMD 2.5 GHz Dual-Core 
Memory: 1.5 GB (Win XP), 2GB (Win Vista/Win 7) 
Graphics: GeForce 8800 (512 MB) or Radeon HD3850 (512 MB) 
Hard Drive: 16GB