[Techtalk] Restoring boot set-up

[David Sumbler]

My hard drive is set up roughly as follows:
/dev/sda1  90Mb
/dev/sda2  45Gb
/dev/sda3  45Gb
/dev/sda5   4Gb
/dev/sda6   4Gb
/dev/sda7 850Gb

Until yesterday /dev/sda3 had my working Ubuntu 11.10 system.  dev/sda7
is my /home partition, and /dev/sda5 is the swap partition.  /dev/sda6
is, effectively, unused.

/dev/sda2 contained an unusable Ubuntu 11.04 installation, which was the
product of a previous abortive attempt to upgrade a 10.10 installation.

/dev/sda1 contains nothing but a /boot/grub folder.

As I have never had much success with upgrading Ubuntu releases,
yesterday I decided to do a fresh install of Ubuntu 12.04 on /dev/sda2.

All - or almost all - went well, and both versions (12.04 and 11.10
on /dev/sda2 and/dev/sda3 respectively) are functioning as they should.

The only thing I did wrong, rather foolishly, was slightly to mess up
the booting arrangement.

Previously, the machine booted to /dev/sda1, which presented a grub menu
giving the choice of the systems on /dev/sda2 and /dev/sda3.  (The menu
is in /boot/grub/menu.lst - does this mean that it is using Grub v1?)
After making the choice, I would be presented with another Grub menu
from the chosen system, and these would be updated with new versions of
the kernel from time to time.  These menus definitely use Grub v2, which
I find much harder to get my head around than v1.

Unfortunately, I told the 12.04 installer to put grub on to /dev/sda.
So now I am presented with a single grub menu, offering the choice of
Ubuntu 12.04, or 11.10 with the latest and several older kernel
versions.  This is OK, but I much preferred the old arrangement.

Before I try to rectify things, and run the risk of screwing everything
up (Grub always scares me, especially version 2!), can someone with more
knowledge and confidence than I have tell me exactly what steps I need
to take to restore the old booting arrangement?

Thanks in advance for any help and advice.

David