Q I have tried to install Ubuntu on my old HP Pavilion Notebook. Since I was short of disk space (and still need Windows) I installed it on a USB disk drive. The install went well, but rebooting produced a Grub error. I now understand from reading around that some old machines do not allow booting from USB, indeed there is no USB option in the BIOS (or Smart Boot Manager). So I restored my Windows boot sector with the MS recovery disk, which is now fine, but leaves me with a USB disk that is loaded up with Linux (fully intact from what I can tell), without any possibility of use.
As Linux advocates this must must annoy you as much as me! I was wondering - since my machine will boot from a floppy disk, is it possible to put some sort of Linux kernel on a floppy that would boot Linux but access the redundant disk for the bulk of the Linux applications (perhaps even the graphical user interface)? I see advantages to this over the Live DVD, in that I could maintain my changed preferences etc and augment the distro with other applications I would like to have. Is this a viable option? I would greatly appreciate some advice.
A This is not just annoying from a Linux perspective: if your computer won't boot from USB, the operating system is irrelevant. However, USB booting is a source of great frustration, as not only is the computer's BIOS a factor, but some USB devices work better than others, so there is much trial and error involved. It would appear that you installed Grub to your hard disk, so the system at the time of installation sees the hard disk as the first disk and the USB disk as the second, but when you try to boot up, the second (USB) disk is not there, resulting in the Grub error (which is almost certainly a "disk not found").
It looks unlikely that your computer supports USB booting if there's nothing in the BIOS, but some computers do provide a boot menu if you press a key (usually delete, F12 and F2 are most commonly used) immediately after starting up. Unfortunately, there is no standard for this, so you'll have the read the manual of watch the power on messages to see of there is such an option, or try holding down a different F key each time you boot until you strike lucky. You have ruled out the use of a Live DVD, but many of them have an option to mount a USB drive as your home directory, enabling you to save your documents and settings and even install extra software, although there isn't much that something like a Knoppix DVD doesn't include.
If your computer really doesn't support USB booting, this would seem a better option than using an unreliable floppy disk. Boot from a Knoppix CD or DVD, plug in a USB drive and select the Menu item Knoppix > Configure > Create A Persistent Knoppix Disk Image. Answer the questions, and it will create a file called knoppix.img on the disk that contains your home directory and settings. When you reboot, Knoppix should detect this file and ask if you want to use it, or you can specify the location by typing
knoppix home=/dev/sda1
at the boot prompt.