On my Windows 7 Ultimate system Norton Security keeps getting corrupted and Windows doesn't detect it anymore as a security program. It also won't start and keeps trying to repair it self. A remove and reinstall works for a couple of reboots but then the cycle begins a new. Never had this problem with Norton 360 which this replaced. All my other systems which run on Windows 8.1 work fine with NS. Most programs are installed on all my systems. Only thing extra on this machine are the games because this is my gaming pc and all the other ones are laptops with Windows 8.1 Pro.
Other security programs which are installed default on all my systems are Malwarebytes Pro and Anti-exploit free version.
Currently running one of my Symantec Endpoint Protection Small Business licenses on this system which seems stable. Ran both Norton Power Eraser and Malwarebytes. Both didn't find any issues.