sorry for the late coming guys, I had some very busy day.
Here's now on the anwers : My pc is some year old but still pretty powerful I believe :
Intel I7 860
raid 0 dual sata disk with plenty of free space
Windows 7 with a quite old installation (I mean, years!), but all still works quite well, I'm used to keep my pc clean (what a wonderful Os win7 is).
The crashes I experienced came in 2 different periods, to be more precise :
when first came out the "new" chromium based opera it was all good and well (can't say for how much time), I kept installed both 12.17 and new one, but really never used the new one a lot..12.17 was still my main browser..I used the "new" only for websites not working properly on the old one.
with Opera 24 I noticed it started freezing the pc, like I said in my first post.
I tried obviously to uninstall and reinstall, but with no result, so I came to the end decision to whipe opera 24 from my pc.
I've then done some month with only Opera 12.17, but then some often-used website started hanging on the old Opera (Facebook), so I decided to try again the new opera..and it just went out Opera 25..installed by mantaining the old Opera..BANG, again the freezes, and this is the moment when I decided to come here and write .
BUT THEN..Took my courage with both hands and decided to uninstall old opera, and keep only Opera25 + Opera mail.
Wanna know ? It is from that day that the pc doesn't freeze anymore..(it's since october 19).
I will keep my eyes opened and report to you if in the next days still works well , of it starts hanging again..I really wish not.
Anyway for now the only relation I can see with the freezes, is the simultaneous installation of both opera on the pc (and pay attention..not necessarily running both at the same time..also running only the NEW one caused the freezes..instead, running only the old 12.17 never caused freezes, even if both old and new were installed).
Wish it can help someone else with my situation.