BartPE Is something I have been using for a couple of years now, and it is one of the best and most useful tools that I have in my collection.
Basically it's a Live CD for Windows. It is similar to WindowsPE but is very hackable/customizable. I use it to boot up computers that are having problems booting into Windows off the hard drive, and recover data or get a backup image of the drive. I also have many different Network tools and other tools loaded onto the "Live" version of windows so I can pop it into a computer and have a whole list of tools at my disposal. Now, I know that there are other "security tool" Live CDs out there already, Knoppix is a really good one, but this is Windows so it's easier (for non Linux geeks) and gives you more flexibility in a Windows world.
Barts out of the box is pretty basic (it has a simple custom shell), but there are several add-ons that will make it look and act just like windows. There are several sites that are dedicated to plugins for Barts. There are also several spin offs that use Barts as a base, but have there own system of plugins and setup. You can also create your own plugings from normal windows programs.
All in all Barts is VERY powerful and VERY useful. I might add some more posts going into some detail about how I have my CD setup, but to get started check out the links below.
Main BartsPE site:
http://www.nu2.nu/
Plugin Sites:
http://oss.netfarm.it/winpe/ (Check out XPE!)
http://www.drowaelder.de/winpe/PEIndex.htm
http://www.911cd.net/forums/ (Take a look at the plugin section)
Spin Offs:
http://reatogo.de/REATOGO.htm
Help:
http://www.911cd.net/forums/
http://www.nu2.nu/pebuilder/help/english/
