Sarge (3.10) New Install - Grub problem

[Chris Robinson <chris@krc.org.uk>]

Hi

I was running woody on my hda disk (120GB).  I got a new disk 20GB(hdb).

So I thought I would run Sarge on hdb, and  mount my woody disk as 
required to get any files I needed.  I therefore do not need dual boot.  
I can install Sarge (3.10) fine but then I get to the question of where 
to install grub.  I just want Sarge to run from hdb

I have tried a number of different answers to the grub question, but I 
always get a grub error, when rebooting.

How should I tell grub where to load itself?

Regards

Chris