I've just tried puppy linux for resizing a partition, but it would also be useful for anyone if their hard drive fails or their operating system stops working.
It loads from CD or USB into memory, is only 130 megabytes, autodetected everything and was very user friendly (apart from having to download a browser).
If you get it and burn it to a CD then if something goes wrong you can get on the internet and find out how to fix it or order a new drive.
Other versions of Linux can do the same but most are larger.
If you download something or change settings you can save it on a USB stick or apparently on the CD.

http://www.puppylinux.com/
(I used the Lucid Puppy version).

 

Yeah, it's a good tool but...

You also got

Damn Small Linux

and

Ultimate Boot CD

and

Ubuntu Mini But that is more of a start for a distro installation...

 

Yes, <snip> Small Linux looks like a good alternative to Puppy and the Ultimate Boot CD would be a good add on to either.

 

I've been messing a bit more with Puppy and I've now got it set up on an old Compaq I found in the street. 500MHz, 256MB of ram and a 10 Gig hard drive.
I've managed to set it up so that it boots from a 4 Gig USB stick instead of the hard drive and the swap file is also on the USB stick.
The performance isn't great by modern standards, but on a machine this old it's pretty good.
Now it runs very quietly and probably uses hardly any power so I could leave it on all the time. Now I just need to think what to use it for.
I'm just about to set it up so I can connect to the desktop from my main PC, I've done it before, so it should be easy.
<ed> Success! Second screenshot is running in a remote desktop from my main PC. </ed>