I have a new Acer Aspire (257 running win 7) that I just received today. It won't stay off. I've tried shutdown from the start button as well as holding the power button down. For some reason it starts itself right back up.
I removed and replaced the battery and it stayed off, but once I started it back up, it's back to doing the same thing.
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Contact Acer and get a DOA, I suspect the power button is faulty.