Computer stopped working after the installation of an antivirus

Greetings,
The use of a computer is new to me. I have recently purchased one, but I am not groomed well in using a computer. I want to download an antivirus on my system. A friend of mine recommended me to use eset smart security 5. It's a month now that I installed this antivirus and it was working up to the mark, but all of a sudden, it stopped working. A message appears on the screen, which says to remove any other antivirus, if installed into the system. I had also installed the Norton antivirus. As directed by this message, I removed the Norton antivirus and now I am again trying to install the eset antivirus, but it always gives me an error code. The error is 2878.
Does anybody know what this error means?
I don’t even have the slightest idea as to what it is.
Please lend me a hand to solve the query.
Thanks.
