Well given the details you have provided, you could be facing a few things. One could be a "new" computer in which someone installed a free trial of windows 10. Another could be a virus. I forget the logistics of the virus but it is something like "Windows is not genuine, call this number to activate or click here or something. The popup is nearly impossible to get rid of, and makes the computer pretty useless. Theres not much on the internet how to get rid of it, but I had a customer bring me a computer like this. What I did to get rid of it was I right click taskbar>Taskmanager> and you find the program that is causing the problem. You then terminate the program or "end task" I then clicked "open file location" and just deleted it. This enables you to go backup your stuff and do what is in the link below. i
http://www.cnet.com/how-to/clean-install-windows-10/
This will reinstall windows 10 and have you start fresh as if it came out of the box.
I truly think this is your problem since you said the computer is new. But to continue with other possibilities, you could be facing a windows trial. Now Microsoft fucked everyone over by not requiring a product key to be stuck on computers anymore after windows 7. Unless your one of those people that saves the boxes the computer came in there not much you can do. But you can use this
http://downloads.tomsguide.com/ProduKey,0301-26388.html
This will find your true windows product key if your computers operating system is Legit. You also want to do this before reinstalling windows 10 as recommended above.
If your computer ends up being a trial which I highly doubt because Acer doesn't sell new OEM computers with trials, you can A either hack it which puts you at risk for viruses and fraud, B consult Acer about the problem, C take it somewhere where someone actually knows what they are doing and can assist you in person then just random people like everyone here guessing over the internet, or D buy a copy of windows and reinstall it your self which i Highly DONT RECOMMEND because I doubt you were given a trial computer but do it as a last resort after trying everything I have said first.
Good luck, if you have any questions or concerns comment below and I will get back to you within 48 hours.
--EDIT--
Alot of people are saying that computers come without operating systems. Almost every computer that is preinstalled with windows 10 come activated. Another thing is as you have stated is you have had the computer for 4 months. Microsoft Windows 10 trial is 90 days, all the more reason you seem to have a virus.
.