I'm sure many of you have encountered the same problem I was facing. I have a portable provided by my employer, but the employer does not provide any means of making backups of this portable. I know, he should, but hey, nobody's perfect.
In the past 6 years I've been working for several clients, gathering a lot of data (code, documents, presentations, you name it). The past 2 years I've been doing some Biztalk work as well, working with virtual machines. Using virtual machines is ideal when doing Biztalk work. No need to pollute your perfectly running portable with Biztalk Server 2004 and visual studio. Working with virtual machines also enables me to work with different versions of Biztalk Server.
An unpleasant side effect of using virtual machines is that they tend to take a lot of space on your hard drive and you'll need at least 1,5 GB of memory in your machine.
As a result, I gathered 30 GB worth of data and virtual machines and I wanted to synchronize this with my recently purchased My Book. In the past years I've used several "free" tools for this (robocopy, rsync, ...) but none of them were satisfiable. Today I came across DSynchronize. This small, free tool has no problems with sync'ing my portable's hard drive with an external drive. And it is doing it fast as well.
I love it!