It’s hard to call an entire OS a “utility”, but Knoppix, a distro of Linux on a live CD, has come to my rescue many, many times. By far, the most common situation I find myself in where I am using Knoppix is when I’m faced with a Windows box that gives me a bluescreen on boot due to missing or corrupted boot files or virus problems. I simply boot from the Knoppix CD, plug in a flash drive, and copy all of the data I can from that NTFS partition. Once I’ve saved the data, I can reinstall Windows to fix the problem. And of course, being a distro of Linux, Knoppix allows you to do far more than just copy data. It’s definitely a CD or DVD everybody should have.