Windows Explorer in Windows 7, by default will not expend the sub-folders on the side navigation. Unlike in Windows XP, when you select the folder say under My Documents, the side navigation will auto expand all the sub-folder that are under My Documents. This is not the case anymore in Windows 7, instead it just shows the root level directory Documents, Music, Pictures, Videos etc. So every time if you want to go jump between the sub-folders you either need to jump back to the previous level and find the folder you are looking for or click the drop down arrow to expand the folder.
Thankfully there is a way to bring the old trick back in Windows 7. Go to Folder Options … Check “Automatically expand to current folder” and apply the setting Now whenever you are on the sub-folder you can easily navigate between other folders.