It's a little program is called synctoy.
I've always been fairly good about backing up data. I've never had a catastrophe either. Once it was easy enough using CD's. Then, I needed the extra heft of a blank DVD in order to keep backup data. Not long ago, however, I've found that even 4.7 gigabytes isn't enough. For example, my digital picture folder is larger than that.Additionally, I was never a fan of keeping data in a proprietary format. The OneCare Live solution, in which Microsoft is getting its feet wet for subscription services, can do backups. Yet it keeps everything deep inside of a large unreadable file format. I want to keep access to a group of usable files.
Keeping data consistent between my backup external drive, my main PC, and notebook has become a snap with synctoy. It works like xcopy used to in DOS days but it roars along with an easy-to-use Windows interface. Click the thumbnail image to visit the synctoy download page.
(The only reason that might keep anyone from quickly jumping on the bandwagon, is the fact it requires the microsoft.NET framework ver 1.1 on the PC. Some people with dial up could find that 22 megabyte upgrade difficult even though it's also free.)