It is curious isn't it.

I did successfully open the BOOT.INI file in notepad as you suggested but the result was not what I expected. On my work laptop, the file looked exactly the same as yours. On the new HDD it was as follows:

[boot loader]
timeout=5
default=C:\$WIN_NT$.~BT\BOOTSECT.DAT
[operating systems]
C:\="Microsoft Windows"
C:\$WIN_NT$.~BT\BOOTSECT.DAT="Windows XP Installation/Upgrade"

The C: drive on the desktop also has a BOOT.INI that looks correct. The one on the new drive appears to have incorrect or missing lines under the [operating systems] section.

I have reread the article you posted before, and whilst it explains the lines, I am no clearer as to why that might be happening.

If it thought it was a slave (back to my earlier concerns about where to place the drive) then it might not expect an OS and therefore not need those entries?