Comment 17 for bug 414996

After many successful 32 bit Karmic installs from a live usb stick to usb
sticks and usb hard disks, I installed a 64bit Karmic from a CDROM (to a usb
stick) and clicking on the Advanced button, noticed the difference in the use
of (hd0) for the boot location instead of an actual device (e.g. /dev/sdb).
I retyped the correct device (/dev/sdb) and avoided wiping out the Windows
mbr (which was on /dev/sda, and which the device.map was mapping to hd0).

Regardless of the install media (usb stick or CDROM), grub-install gets all
the devices wrong in device.map (in this situation).
As a result of the device.map file mapping the Windows sda to hd0, every
device mentioned in the grub.cfg (or menu.lst) is wrong too, even when the
mbr goes to the right location. The boots only work because of the use of
UUIDs. To fix the grub.cfg file, correct the device.map, and rerun update-grub.
e.g. Make hd0 the actual boot device (/dev/sdb), and put the windows /dev/sda on hd1,

if you want to allow the usb stick to boot windows when used on another computer,
edit the grub.cfg to remove the UUID lines for the windows menu items.

See bugs 45989, 46520, and 384633 for some history of using the wrong
device for the mbr.