hallo
i tried to play at 1024x600 but the game doesn't use this res, it seems to work at 1024x768.
Inside config.idv the resolution is correct. and now what could i do?
do you think to fix this ?

It seems DD has several menus / screens that don't scale to the netbooks unusual resolution. The map/logs/quest screen apparently have three default resolutions like the start menus. I feel sure it is the 1024 horizontal res that makes the game use the higher res menus and dialogs which are clipped by the 600 vertical res.
I doubt this problem will ever be fixed due to the age of the game. . . =(
Edit: Will the netbook allow you to play on an external monitor?

yes i think the same
i tried many resolution hoping something would happen...1023x600 1023x599 lol and others but nothing.
yes is possible but i can't carry with me my heavy crt...

Unfortunately I believe that as the game is made up of sprites it is just a collection of different sizes of sprites to match the few main resolutions it allows. Hence that is why the interface wont scale well. It is simply not designed to be able to be used in these resolutions so its a problem that would in fact be difficult to fix, but that doesn't mean you shouldn't hold any hope. When DD was released on GOG it was in fact the Larian team, the actual creators of the game who upgraded the game and did in fact allow support for a few more resolutions than the original game had allowed. Here is a link to the Larian post about the changes that were made, if you want a few additions id head over to their suggestion thread and see if you can twist their arm so to speak ^_^

Bottom line . . .
If your default vertical resolution is 768 or greater
You won't have this problem. You can input and run higher resolutions with the only noticeable change being your start menu and map/quest menus displaying at 1024 x 768 regardless of the game resolution. The game itself will display and run at the selected/input resolution with menus size displayed at the maximum 1024 x 768 resolution. The higher the game resolution the smaller the start menu and map/quest menus will be with game play unaffected.
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If your default vertical resolution is less than 768 (usually found on netbooks i.e. 1024 x 600)
You will need to play at 800 x 600 or 640 x 480. Higher resolutions will result in clipped menus. See attached image.
The game selects a menu size based on the horizontal resolution. A netbook using a 1024 x 600 game resolution causes the game to use the 1024 x 768 menus which will be clipped by the 600 vertical resolution. Selecting 800 x 600 or lower will allow the game to select the default 800 x 600 or 640 x 480 menus which will not be clipped.