Upgrading from osticket 1.2 possible???

We have a very old (but working) installation of osticket 1.2, and are about to move on to eticket.

I have tried the upgrade.php way, but I get a lot of errors doing so:

Code:

Upgrade
Step 3:

Database connection established...

Found database...

Initializing database...

Running queries from 'upgrade-1.5.9.sql'... (skip to end)

Error: Unknown column 'banlist' in 'ticket_groups'

Error: Unknown column 'db' in 'field list'

Error: Failed: Table 'helptest.ticket_settings' doesn't exist

Error: Failed: Table 'helptest.ticket_settings' doesn't exist :
DELETE FROM ticket_settings WHERE `key` = 'accept_attachments'

Error: Failed: Table 'helptest.ticket_settings' doesn't exist :
INSERT INTO ticket_settings (`group`, `key`, `value`) VALUES (NULL, 'accept_attachments', '0');

Error: Failed: Table 'helptest.ticket_settings' doesn't exist :
DELETE FROM ticket_settings WHERE `key` = 'answer_method'

Error: Failed: Table 'helptest.ticket_settings' doesn't exist :
INSERT INTO ticket_settings (`group`, `key`, `value`) VALUES (NULL, 'answer_method', 'pop3');

Error: Failed: Table 'helptest.ticket_settings' doesn't exist :
DELETE FROM ticket_settings WHERE `key` = 'attachment_size'

...and so on...

When I compare the database content of our old database and a fresh install of eticket 1.7.3 they are very similiar, with a few exceptions (see the first few error lines for example).

So my questions are: is it possible to upgrade from osticket 1.2? Would it be possible to manually change the database to work with the upgrade script?