I've followed the Debian harddisk-upgrade HowTo, changed fstab
according to the above, installed grub on the new harddisk according
to a posting here by Mitchell Laks (thanks for that!).
Then I switched the machine off, removed the old harddisk, switched
the new harddisk from slave to master and turned the machine on.
Grub executed OK, there's a lot of info scrolling over the screen. At
some point there's a message, something like 'mounting /dev/hda1
read-only' (don't know exactly since it isn't logged anywhere)
The next message is where it ends: 'unable to open an initial
console'.