unable to reinstall grub

[Bertrand Haut]

I've just install Windows on my first partition and, of course, Windows has 
overwrite my MBR.

I've booted on one floppy with grub and succeeded to load ubuntu. Now I'm 
trying to reinstall grub. 

with a grub-install /dev/hda, I obtain :
root at neptune:/boot/grub # grub-install /dev/hda
The file /boot/grub/stage1 not read correctly.

I've also reinstall the grub package but it change nothing.

Has somone an idea how to restore my grub ? I don't like the idea to be forced 
to boot in Windows.
-- 
Berti