See, some days ago I got myself Jagged alliance and it wasn't until I switched to graphic mode Direct3D that the game started working properly, without very noticeable sound/video lags and random blurs in cutscenes.
The graphic mode application has five different settings. Does anyone know what they do? What I should pick in a Windows VIsta machine? What's the criteria to pick the best setting, my system or game-dependent?
Cheers to you all.
Edit: the five different settings here are, in this order, Overlay, Surface, Direct3D, DDraw and OpenGL. I believe it was set to Surface out-of-the-box.

You probably should have posted this over in the Jagged Alliance Series forum. Community tech support requests for specific games are usually posted within that game's forums, not in the general discussion forum.
As to your question, its really a matter of preference. Each setting uses a different method for rendering 3D elements, the best of which is likely either OpenGL or Direct3D. With a game this old, you are not likely to see a noticeable performance difference on any setting, since any modern machine has more than enough "muscle" to handle any of those settings, but the overall look should improve. Try each one of them out and pick the one you like the best.

This needs clarification: I did solve this specific problem in the specific forum. What I'm asking here is for a more general guidance. I want to know what makes a difference for each setting in each game.
One thing is for sure: the difference between "surface" and Direct3D is very noticeable in the specific case of Jagged alliance. I'd like to know about other games too though.