File Explorer drags in Win 8

File Explorer has been moving very slowly in Windows 8.1. I'm running a Norton scan, but I wonder if this is a hardware problem or a virus? This is fairly recent.

I've run chkdisk, and defragged both hard drives. No joy.

Search works quickly to find a folder, but navigating between the folders with file explorer has become extremely time-consuming.  I have an 8-core chip and 16G of memory.

Matt