How to keep NIS from loading in start-up, so that I can use another AV program?

Hi, friends.

In the old days, I could download one NIS installer, keep it on my computer, and use it to re-install the program offline, anytime. Nowadays Symantec requires me to go online, use a web installer, and wait one hour on my slow connection, for the program to download and be activated. (I have a monthly download limit of 6GB)

Today I would like to try another AV program instead of NIS, just to compare the two. I assume that, to avoid conflicts, the new program installer will require that I disable NIS 2014 before proceeding, or else, remove it altogether. What, then, would be required to switch back to NIS, I can only imagine: perhaps another complete re-installation, and another hour of using a web-installer and activator.

Is there any way simply to turn off NIS 2014 completely and keep it from loading on reboot, without removing it entirely from the computer? In order to install and test a trial version of the other AV program for 30 days, without facing any conflicts with NIS, I need to know the simplest work-around.