Being able to boot from a USB stick can be very useful – whether to install a new distribution on a netbook, or to have your own portable distribution to carry round with you. More here
It’s possible to do the necessary work to resolve this manually; but far and away the easiest way to deal with the problem is to use the usb-creator program available with Ubuntu. Currently it’s not directly available as a Debian stable package, but you can grab it from Ubuntu by adding this line
