Ok, as long as it works for you... The stuff I get, Norton can't deal with, i used it for about a year. It just blocks up my system.
If you have to change, I suggest Eset, you may like Norton, but Eset is fully configurable to meet special needs. I have some scripts I run that show up as a Virus even though I made them and know they are safe, it's harder to allow them to pass with Norton, Eset I can add them to the exclusion list. Also it finds heavy hitters like Sirefef, where Norton and Mcafee choke on it. Eset chokes on it too, but at least tells you it is in there, the only way to get rid of it is with the Removal tool.
Other than that, Full Security "Suites" like Mcafee and Norton, add in all kinds of extra stuff as well as the AV program, Firewalls, Toolbars, and stuff it loads into IE or other browsers. I switched to Eset cos it had the smallest footprint of all of the AV programs I've tried. Any AV Program will slow your system down, that one does it the least. I always suspect any AV program that takes over Windows 7-8's already adequate Firewalls. Sometimes you need to block an Internet Address, or a Range of Addresses, you can do that with ESET's AV, right from within the program, and it wont affect the Windows Firewall.
I wonder why Norton came up as not compatible with 8.1, you think it was the version you had, or is there a version that works specifically with 8.1?
Anyway, I'm, sure there is a free substitute that will work until you decide what to get, the only one I don't like is AVG Free, Sirefef breaks right through it.