Which of these two inventory types would be the best: Ultima 7/8-style (many storages, items can be moved freely) Might & Magic 6/7-style (one storage, items are in a grid) I guess that most of current RPG''s and adventure games use the last style, but what do you think? Are there any other inventory styles?

Well, there''s also the "list" approach - just list all the contents of the inventory as plain text. It''s still used in some games, and it''s not that bad - it allows items to be manipulated and identified very easily (no "what''s that bluish splat supposed to be?"). But to answer your question, I think the Ultima 7/8 style was a stupid experiment that just made things more difficult for the player (the sacks that you had to use to keep any order looked all the same). I recommend the grid approach, but with some extra storage possibilities like sacks, though (Ultima Underworlds had a "grid", but with container objects).

Painless is right. The easier approach for you and the user is the list-style inventory. However, if you want something more, well, complicated, then you should go for the Might and Magic grid-style inventory. However, as painless said, it becomes difficult to determine what every image represents. So you should include a box that displays the name of the of the item that the pointer is currently over.

"Remember, I'm the monkey, and you're the cheese grater. So no fooling around."
-Grand Theft Auto, London