Hi Dodger.....Take the advice given by Chuck and feel free to ignore any of my comments. Chuck is a top-notch IT Consultant, whereas I only pass-on information; most of which I have established from the real Techies in AB.
You asked which is better....Avast or MSE. Personally, I would opt for MSE.
However, you should not have more than one Virus Protection programme installed because they will conflict with each other and could cause serious problems. Anyway, if you do take your computer back to factory settings, you will have to reload a VPP.; which will not be difficult. If, however, you do not go back to square one, it is important to get shot of one of your VPP's.
I look forward to hearing how things progress.
Best wishes.....Ron.