Sometimes, when navigating in your local folders (in your user profile), it may seem to take forever to open a specific (local) folder, and the green loading bar at the top crawls forth at a very slow pace. If that is the case, try turning off folder optimization.
Windows 7 introduced a new feature called folder optimization, which is basically telling Windows what to do with the files inside a folder, such as generating thumbnails for pictures and videos, reading metadata from documents, reading media information on music, etc. Occassionally, this process can take a long time, and can really slow down Windows Explorer when attempting to browse such a folder.
If you stumble across such a folder, folder optimization may be active, but can fortunately be turned off very easily.
Note that this only works for local folders in your user profile, not network folders, or system folders (outside your user profile).