Dear Gog.com,

I have problems with launching my copy of Duke Nukem: Manhattan Project. The problem I am having is that the game claims I do not have the config.cfg -file at D:\Porgram Files (x86)\GOG.com\Duke Nukem - Manhattan Project\duke\base\config.cfg when trying to launch the game. As my screenshot displays, I actually have it.

So how can I solve this problem?

It worked, thanks! Of course I did not come to think of that, stupid me :p

*Offers digital coca-cola as reward*

Yeah, a common problem when running games, particularly old games, on Vista and Win7. UAC and DEP try to prevent the games from modifying files inside Program Files folders as these are protected folders. Running as administrator forces the system to allow it which is why this works. But even better, just don't install games into Program Files folders, put them in your own folder so that UAC and DEP don't get in the way (e.g. C:\Games\).