QUESTION I'd like to transfer to an external drive the documents, music photos and video stored on my Windows 7 PC. Could I continue to access these folders via the Libraries in Windows 7?
HELPROOM ANSWER Yes, you would be able to continue using Windows 7 Libraries. In fact, this is exactly what they were designed for.
Libraries allow you to organise your files into collections, regardless of where they are stored on your PC. External hard drives can also be used, provided that they appear in the 'Hard Disk Drives' in Computer. Removable storage devices such as USB flash drives do not tend to work this way. If you're intending to frequently access these files, it's worth getting a fast USB 3.0 or eSATA drive to speed up data transfer.
Each Library can contain files held in folders in various locations and on different drives, allowing you to search, sort and share them as though they were in a single folder. Windows automatically indexes the files to speed up searching. You can also share a Library over a network. This is a convenient way to gather up folders which may be located in various different locations and share them as though they were a single entity.
Once you've plugged in your external drive and copied over the files, open Computer in Windows Explorer. Right-click any folder stored on your external drive and choose 'Include in Library'.
From here you can select which of the existing Libraries you would like to add your folder to. You can include a folder in more than one library by repeating the process and selecting a different library each time. You can also create new libraries to house your own categories of files. Note that Libraries were introduced with Windows 7, so if you're running an older version of Windows then you're out of luck.
However, the feature is retained in Windows 8 and a couple of new features have been added. When you create a new Library you can select a custom icon to help it stand out. You can also pin a Library to the Start page so it will appear as its own tile.