So Arjun, thanks so much for your interest. I'll try to flash the tablet after have installed the latest dot net framework as you said. I have to say that i have flashed another tablet with the same computer, in this case my mac, and all went right. I'd also tried with a linux pc and only one thing went better. The usb symbol at start-up appears for more time and not only for just an istant. I don't know what i have to do...