Occasionally, I encounter a folder of photos that takes forever to open. I tried defragging, copying the files to a new folder, and cussing at it. None of these helped, although the last one made me feel better.

Finally found the fix. Incredibly simple, and I felt incredible stupid.

  1. Right click the folder
  2. Select properties
  3. Click the Customize tab
  4. Select "Pictures and Videos"
  5. Click OK

That was it. Then folder opens right away.