The Los Angeles Times has a nice writeup on Damn Small Linux.
Apart from being compact and fast, however, DSL Linux may change the way you use your computer. For maximum speed to rehabilitate an old PC, you can install it like any other operating system, directly on your hard drive, either for exclusive use or as an alternative to Windows. You can also start and run it from a mini-CD, even if the host computer has Windows on it. So when you do visit grandma, you can take your DSL Linux with you.