Oh, so this is not related to Windows. Hehe. I think once you plug in power to the PC, just wait a couple of seconds before hitting the power button. My motherboard automatically powers up before hitting the power button, but after 1 second, it turns off. Only after that, I should hit the power button. Otherwise, my modem is not detected. I have to unplug the modem from the USB cable and plug it back to get it to work. You know, it was very hard to find why my modem was not detected sometimes. In the end, I just figured it out. Anyways, maybe BIOS updates can solve those minor issues.