A failed software install left ours blue-screening on boot due to a corrupted driver. While we've got a USB DVD drive in the house, the R100 doesn't support USB CD or DVD booting. I've spent a goodly chunk of the afternoon trying to find someway of getting it to work.
DUSE, the DOS USB project doesn't work with the R100's USB hardware (though it may well for many other platforms). However, I was able to track down a site with a copy of Toshiba's own recovery boot floppy software - which is conspicuously absent from the UK site.
You'll probably need to add files like SMARTDRV to the disk just to be sure...
It's not just for recovering Windows installs - you can also use it to install Linux or any other OS on your laptop. OpenSolaris, anyone?