Hi all, I think I have found the solution, I didn't post until now because I was waiting to see if it is a definitive solution. The problem was actually quite simple: a conflict between 2 devices sharing the same resource. The difficult part was to find out which devices were in conflict. Windows gave no clue about that, not in the bootlog.txt, nor in the device manager, nor in the events logger. So I have installed Linux and find out the same problem. Luckily Linux gave some more infos: the problem was a conflict between the network card and the modem card on IRQ 11. For now I have deactivated the modem. It is almost a week and found no more problems occured. I could reconfigure the modem to use another IRQ (IRQ 10 seems to be free), but since I don't need the modem I am satisfied with this solution. If somebody has the same problem hope it helps. Bye. P.S.: I had already formatted and reinstalled the os, but it didn't resolve. This is not a case of bad installations and win recovery was not useful at all.