When I updated my oneiric, the update messed up the linux boot altogether.

I have Vista dual boot with Vista primary boot loader.
This time the update left the MBR alone, but grub gave the menu, and every
boot option ended up with "partition not found".

The first time I used alternate install and installed Grub in the beginning of the
root partition. Then the update wrote Grub2 onto the MBR and messed up the Vista boot too.

Guys, I have managed to start to get a look at the files using a usb conection. Bearing in mind this is 12.10 where should I start to look? I seem to be able to look at the files editing may be another problem.

Steve mint does not seem to be available in the Ubuntu SW centre should I need it?

Have manged to get into the system and although some of the problems are stll there despite updating my system I am closing this trhead, thaks to all who helped me. Sorry I cannot be any more specific but I am not sure what let the system come up.