Short post :) I needed a simple way to backup my photos to an external drive and I couldn't find a simple & free solution so I ended up using the Robocopy tool in windows. What you need to do to mirror a directory structure is:

robocopy d:\users\fredrik\desktop\kamera f:\backup\foto /MIR

This will mirror everything in the directory d:\users\fredrik\desktop\kamera to f:\backup\foto. The second part of this is to automate it using the windows task scheduler. It can be found under Control Panel > Administrative Tools > Task Scheduler depends a bit on windows version and installed language pack.

1. Choose to create a Basic Task, give it a name.
2. Choose how often is its to run (once a week is good for me).
3. In Action select Start a program, the path to robocopy is C:\Windows\System32\Robocopy.exe
4. Enter arguments for robocopy in the arguments text box

After this just hit finish and if you want give it a test run.