Further info.
BIOS gives boot sequence as DVD, SSD, hard disk,...
When it went into the recovery environment I carried on to the command prompt. I used chkdsk to see if it could find the disk (where are these commands documented?):
chkdsk D: was the 100MB partition
chkdsk E: was the SSD
chkdsk C: was the new (old!) hard disk
If the OS thinks the HDD is C: no wonder it falls over. But does it and how can I fix this?
2Mb/s? Not in my lifetime! (Nearly true Dec 2011)