If it helps I got fed up with Norton slowing down my PC and popping up reminders to update right in the middle of a Power Point Presentation to a hall full of people so I dumped it and used Kaspersky Internet Security (for the past 10 years now) without any problems.
I also use a software package called 'Advanced System Optimiser' by a company called 'Cleverbridge' which is excellent at removing spyware, adware, malware, all kinds of internet traces and much more. This software (nothing to do with 'Optimiser pro') keeps the PC at peak performance.
[All Internet Security packages will eventually slow down a PCs operating speed] ASO will regularly remove all the temporary internet files that are responsible for slowing everything down and optimise the registry for best performance.
ASO costs around £20 + Vat
contact Email I use for renewals is email@example.com (if it helps)
Now... back to picking the courgettes and tomatoes....JH