Since the Windows 95 day, I've learned the habit of saving my profile data on a drive separate from the where the system is installed. This allows me to completely blow away (reformat) the OS without having to save my data everytime.
On Windows 7 (and Vista, if I remember correctly), this is made even simpler. Simply go to you profile folder where you see your special folders (My Documents, My Pictures, My Music, etc.).
Now, right-click on one of them and go to the location tab.
Browse to you new preferred location, and select Move.
You may have been prompted to merge the contents of you special folder. If you selected no, you may find that you will not have duplicate special folders. That's fine. Simply delete the one that points to the old one (the one on the system drive).
I hope this helps. Enjoy!