I don't go anywhere without a Knoppix CD because it is so useful to be able to boot up Linux when there is some sort of problem with a Windows machine and perform some maintenance.

It can fix drives, reorganize partitions, even virus check your machine.

There's a convenient guide to Computer First Aid with Knoppix if you want to see the sort of things that can be achieved.

Knoppix should certainly be part of an administrators toolkit, and the above is a good guide to why Knoppix can be so handy.