One thing you can do is change the default starting location for Windows Explorer.
Method #1:
Start > All Programs > Accessories > Right Click "Windows Explorer"
Change the target field from:
%SystemRoot%\explorer.exe
to
%SystemRoot%\explorer.exe /n, /e, <New Path>
i.e. %SystemRoot%\explorer.exe /n, /e, %USERPROFILE%\DropBox
or %SystemRoot%\explorer.exe /n, /e, C:\Users\username\DropBox
Method #2:
Shift+Right Click the Taskbar Icon > Properties
Now follow the rest of the process as you would with the above method.
Otherwise, you can create a toolbar and place a shortcut to that folder within the toolbar.