Thanks for your help!
I have already got Ms essential on my Laptop. I also downloaded avast last night, but none of them seem to remedy the problem. I can cope with the sudden sound, but explorer becomes very slow since this incident. Please help
You mentioned pop-ups. What do they say? It's possible they are coming from your computer, but they could also originate from websites you are visiting if you don't have Ad-Blocker or a program to control scripts that are designed to run when you access the site.