Installing and upgrading help

Hello.
I'm upgrading a Moodle installation (1.6 >> 1.9) & on the new version there is no site Admin block on the front page.
I don't know if there was one on the previous installation as it's not my Moodle.

I'm getting a 500 error on the link:
http://thesite/moodle/admin/index.php

I do get to:
../admin/settings.php?section=locationsettings
../admin/settings.php?section=themesettings
../course/index.php?categoryedit=on
../admin/user.php
etc
but not the main admin page.

Any ideas on how to restore the block would be appreciated.
Thanks.