When you open, save or browse for a file, Windows opens a “Common file dialog box” containing a few shortcuts in left side pane which is called “Places Bar” and the shortcuts are called “Places“.

To customize these follow the next steps:

1. Type regedit in RUN dialog box and press Enter. Go to:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies

2. Right-click on Policies key and select New -> Key. It’ll create a new key, give it name comdlg32. Now again right-click on this new “comdlg32″ key and select New -> Key and give the new key name Placesbar. So the final key path would be:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\comdlg32\Placesbar

3. Select Placesbar key and in right-side pane, create a new String value Place0 and set its value to your desired path. You can set it to a drive like C: or you can set it to a particular folder like D:\Wallpapers. You can also use some predefined values to put system elements in Places Bar:

MyComputer
MyDocuments
MyMusic
MyPictures
MyNetworkPlaces
MyFavorites
CommonDocuments
CommonMusic
CommonPictures
Desktop
Printers
Recent
ProgramFiles

You can set up to 5 places. So to change other default places, create new String values Place1, Place2, Place3 and Place4 and set their value to your desired path.

4. Now you’ll see your desired places in common file dialog box. No restart needed.

Source: How to Customize Default Places Bar in Windows Common File Dialog Box?