These things can be found in an increasing number of systems today. One can put a floppy drive, a secondary battery, or an IDE device in it. Since there's a USB floppy with this toshiba, one CD or DVD module and an 'empty' module (to reduce weight without the risk of damaging the SlimSelect bay) are sold with it.

Since it can be hotswapped, it's nice to know that Linux also supports hotswapping. You'll need some extra tool to register and deregister IDE-devices; you can find it at http://users.ox.ac.uk/~univ1377/. There is also a debian package of which you can simply apt-get. Although written for a Dell C600, it works on this system too. I don't think there's extra kernel-support needed, but might be wrong there.

It's a nice 'n' simple program to user. To remove a device: unmount it, run hotswap, take out the device. To add a device: run hotswap, insert the device, and mount it.