Well, it's official: managed to finish the game without ever having a crash! Computer had the following configuration: AMD sempron 3400+, 2Gb RAM, 350 Gb HDD, nvidia 8400gs 512 Mb RAM, something that came in a box with mouse and keyboard for the equivalent of 150 euro with a 2 years warranty in my country. XP installed.
Problems seem to me to have been caused by the fact (well-tested) scripts/scenarios paths were not respected by me previously.
For those of you that wish to know how it ends, or to compare choices, you have a saved game attached. Plenty left to do.
Once again thanks to the guys that have put together the unofficial patch. If only a map editor would have been released with the game...