What happen if I download Ares in my computer?

I don't know what "Ares" is, but if it purports to help you download pirated content, then it certainly is not safe.

PauNegrete wrote:

I want to download free music and videos to my computer

There is no way to safely download stolen content. If the "free" music and videos you are referring to are actually commercial music and videos that you are trying to get without having to pay for, that is extremely risky behavior. Many people these days are getting infected with nasty stuff on their very first attempt ever at downloading stolen content like this!

So, even if you don't feel particularly bound by ethical and legal considerations, you should avoid such things for your own safety. You should not download and open content obtained from a criminal any more than you would swallow a pill handed to you by a stranger on the street.