My Acer Aspire 4520 is able to boot after being without power for about 1 minute, and it runs smooth, but it just fails to reboot. It should be related to BIOS, since if I insert the CMOS battery, it won't boot at all. I tried to enter BIOS setup after the first boot and just save everything as standard, resulting in an instant-reboot, but still no POST. I've been troubled about the laptop for a month, but still haven't found an solution. Another thing: It's unable to boot when then default power battery is present, even if the cable is plugged. I can only make it boot without any kind of battery present, and only the power cable plugged. I can then insert the power battery and it will still function until it is shutdown. But it still can't reboot, no matter how I it. Even if I just hold the power button until it turns off and instantly turn it on again. So, does anybody have an idea what I can do?