re-installing grub (lvm)

[Mathieu Malaterre <mathieu.malaterre@gmail.com>]

Hi all,

  After installing Windows 7, I lost my grub installation. I would
like to repair my grub installation. I prepared a bootable USB key
with a squeeze netinst iso. I can boot into 'rescue mode'. After
network autoconfiguration I can go to a shell, but when I type:

# grub-installer /dev/sda

It reports:

chroot: can't change root directory to /dev/sda: Not a directory

  Disk is simply: Win7 as primary partitation and the second one is
simply an LVM with /root, /home, / and swap (in this order).

Thanks a bunch !
-- 
Mathieu