http://community.acer.com/t5/2014-Archives/How-do-I-access-the-BIOS-on-a-Acer-Aspire-V3-571G-9636/td-p/13751 tells about different keys (f2 and delete, possibly depending on the model) and different starting points (turned off versus just shut down).

Moreover, not booting up can mean different things for different people. The definitions range from "nothing at all happens when I press the power button" to "clicking my username on the Windows welcome screen gives an error message".

So please tell more about the situation, what you do and what happens.

Kees