Well, it seems that more or less the problem is moderately solved, as I've been playing for more than 1,5 hours and any problem. What did I do? Everything you've see, and other things that I do not think have any influence on the subject (defragmentation, files erase, etc). One main change I've done is that I asked for a friend its EU2 version (it's Strategy First one, which it seems to be the Northamerican one).
Now, I'm playing in 60Hz. So I don't know if it coulb be either the version, but I do like more this one as there are some options I couln't do with Spanish one.
So, at the moment, everything's going on...
But I'm sure there's a problem in the computer... I'll try to take it to a technician...
Thank you very much again... without your aid and interest (specially to Castellon, who, by the way has a nick like a city in my region in Spain... don't know if this is the reason), and hope to see you in other threads and not Tech Support any more (that would be very good news)