Installing ubuntu on a USB hd

[Francesco Zamboni]

Hi to everybody...
I'd like to install the new ubuntu (that I like really a lot) on a usb hd, to being able to use it for maintenance with the hundreds of (cd-less and floppy-less) pc I've to administer (thing that at the moment I do it with a knoppix). 
Now, I successfully installed it on that external drive, but it refuse to restart going on kernel panic. I presume the cause is being unable to load usb drivers before attempting to mount root... on the net I've found scarce documentation on how to proceed rebuilding the initrd to include that drivers... somebody could point me to some resource on the web, and tell me if ubuntu has some particularity in this regard?
Also, I would like to suggest to the developers that including this option directly from the installer could be a cool feature for ubuntu... from a systemistic point of view, having a complete personalized linux distribution on usb hd to be taken around would be unvaluable, even more than a on-cd one....