The library folders where your documents, music, videos, contacts, etc are stored in are located in the users' folders by default. This is fine as long as you have everything on your computer on just one partition, but it may be helpful to relocate those libraries if you want to split your operating system from your data files on a separate partition because these folders tend to become the largest on the average home computer.
Before you start moving, you need to create new folders that will be used as libraries later on. Go to the location where you want to move your libraries to and create folders to replace the old ones (Desktop, Downloads, Favorites, Links, My Music etc.).
Now to get going, open your user folder, in my case that's C:\Users\christian. This is where the library targets are that you want to move. Start with any of them and right-click it, then click on Properties. On the Location tab, you'll see the path to the folder that the library is using right now, which points to our Users folder:
Click on Move... and a folder browser appears. Browse the corresponding folder that you have just created and click Select Folder. Now click Apply - if you had files in your old library target, it is recommended to move them to the new folder; Windows will do this automatically upon clicking Yes on the appearing prompt:
By default Windows installs all programs into the C:\Program Files and C:\Program Files (x86) directories. If the hard drive you have the operating system installed on is running out of space though, or you just want to have the OS on a separate SSD, you might want to consider changing these default installation paths.
Be warned before you go on though! Microsoft does not officially support changing installation directories (see here). You are responsible for all consequences.
Furthermore, since we are going to edit the Windows registry for our causes, you should have that backed up first in case something goes wrong. Here's how: http://www.faqforge.com/windows/backup-your-windows-registry/
Now that you have been warned, let's get started: Open a Run... prompt and enter regedit. I will be referring to our new installation path as E:\Program Files and E:\Program Files (x86), so replace these paths with the ones you want to have (you can choose other names as well). Now browse the left registry pane for the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion key. Click on that key once to show its contents and locate the ProgramFilesDir and ProgramFilesDir (x86):
Double click those values and change C:\Program Files to E:\Program Files as well as C:\Program Files (x86) to E:\Program Files (x86). Furthermore it might be safe to change all other paths directing to the old directories to point at the new ones as well. That's it if you are on a 32bit system, close the registry and reboot your computer.
64bit users have one more step to go. Close the registry and open another Run... prompt. This time, enter %systemroot%\sysWOW64\regedit. Another registry windows will open. Repeat the exact same steps here that you have done before. Afterwards, close the registry and reboot your computer.
When you set Windows 8 up you were given the choice whether you wanted to allow applications to read your locality or not. If you made up your mind towards the choice you have taken you can still change that setting whenever you want to. To get to it
1. open Charms by hovering your mouse to the top right corner
2. open the Settings charm
3. click on Change PC settings on the bottom of the panel
4. click on Privacy
5. change the first switch's position to your likings: