External HDD Syncing

I'm looking for some suggestions on the best way to sync up a couple of USB external HDDs (OS: Windows XP). One of them is my primary external drive. The other one will be used as a backup of the primary external.

I would like the whole process to be as automated and simple as possible, but it doesn't have to be real-time. In fact, it would be better if there were a few hours delay between the two.

It probably sounds like I'm a little paranoid, but there are some legitimate reasons for this :D .

I use & love treecomp http://lploeger.home.xs4all.nl/TreeComp3.htm

I use & love Free File Sync -> http://sourceforge.net/projects/freefilesync/