Copy one of the .mod files (or all of them) to the folder that contains the adventures. The path to the folder is usually as follows:
Users\Public\Documents\The Witcher(Windows Vista\7)
or
Shared Documents\The Witcher (XP).
Now, rename the extension: .mod -> .adv
e.g. ice_plains.mod -> ice_plains.adv
Now start Djinni, choose Module, Open Module and choose: ice_plains.adv.
You can open the area, see the area properties, placeables, triggers, sound objects, waypoints and actionpoints. Actually, you won't be able to see any scripts.
If you click on a trigger and try to open a script by clicking the NSS icon, you will see nothing, or rather:
void main()
{
}
because all the Witcher scripts are compiled.