I purchased the Avast Professional Edition on-line and followed all guidelines for installation. At a point, Avast required a system restart after updating and I allowed it. At start up, I got the message that Windows Explorer has stopped working. I then launched it through the task manager. This I now encounter at every start up. Pls who could help?
Welcome to the forums, kennysteve. 
What av program was on your computer before avast and how did you remove it?
Kaspersky was there and I removed it using the Kaspersky program uninstall