Since there are several different ways to open files, perhaps it would be good if you would describe in detail exactly how you're trying to open files.
I can assure you Photoshop CC can be used to open more than one file at a time on Windows 8. And as far as I know that doesn't require any special configuration.
If you use 'Open With' from Windows Explorer, I think you can only open one file at a time. Bridge works fine though. In fact it can get you into trouble if you have a lot of files selected, and are daft enough to hit the Enter key.
Some choose not to use Bridge. I don't care for it myself and don't even have it installed. With a thumbnailing shell extension installed File Explorer makes a nice integrator.
From File Explorer, Open With does not appear when multiple files are selected.
Dragging and dropping to a Photoshop shortcut on the desktop works, as does dragging to the Photoshop Taskbar button and hovering (which brings Photsohop to the front if it's already running) then dropping on the edge of Photoshop.