5.7 > 6.8 error on upgrade

I tried upgrading a copy of site on my local pc from 5.7 to 6.8

I got these errors on running update.php

* user warning: Column 'vid' cannot be null query: UPDATE drupal_term_node t SET vid = (SELECT vid FROM drupal_node n WHERE t.nid = n.nid) in C:\wamp\www\yeawo\modules\system\system.install on line 1150.
* user warning: Duplicate entry '5433-2182-' for key 'PRIMARY' query: ALTER TABLE drupal_poll_votes ADD PRIMARY KEY (nid, uid, hostname) in C:\wamp\www\yeawo\includes\database.mysql-common.inc on line 374.
* user warning: Duplicate entry '1-0' for key 'PRIMARY' query: ALTER TABLE drupal_term_node ADD PRIMARY KEY (tid, vid) in C:\wamp\www\yeawo\includes\database.mysql-common.inc on line 374.

and further

Update #6043

* ALTER TABLE {flood} ADD INDEX allow (event, hostname, timestamp)
* ALTER TABLE {history} ADD INDEX nid (nid)
* ALTER TABLE {blocks} CHANGE theme `theme` VARCHAR(64) NOT NULL DEFAULT '', ADD UNIQUE KEY tmd (theme, module, delta), ADD INDEX list (theme, status, region, weight, module)
* ALTER TABLE {blocks_roles} ADD INDEX rid (rid)
* ALTER TABLE {filters} DROP INDEX weight
* ALTER TABLE {filters} ADD UNIQUE KEY fmd (format, module, delta)
* ALTER TABLE {filters} ADD INDEX list (format, weight, module, delta)
* ALTER TABLE {node} DROP INDEX status
* ALTER TABLE {node} DROP KEY nid_vid
* ALTER TABLE {users} ADD INDEX mail (mail)
* ALTER TABLE {users_roles} ADD INDEX rid (rid)
* ALTER TABLE {aggregator_category_feed} DROP PRIMARY KEY
* ALTER TABLE {aggregator_category_feed} ADD PRIMARY KEY (cid, fid)
* ALTER TABLE {aggregator_category_feed} ADD INDEX fid (fid)
* ALTER TABLE {aggregator_category_item} DROP PRIMARY KEY
* ALTER TABLE {aggregator_category_item} ADD PRIMARY KEY (cid, iid)
* ALTER TABLE {aggregator_category_item} ADD INDEX iid (iid)
* ALTER TABLE {contact} ADD INDEX list (weight, category)
* ALTER TABLE {poll_votes} DROP INDEX nid
* Failed: ALTER TABLE {poll_votes} ADD PRIMARY KEY (nid, uid, hostname)
* ALTER TABLE {term_data} DROP INDEX vid
* ALTER TABLE {term_data} ADD INDEX vid_name (vid, name)
* ALTER TABLE {term_data} ADD INDEX taxonomy_tree (vid, weight, name)
* ALTER TABLE {term_node} DROP PRIMARY KEY
* ALTER TABLE {term_node} DROP INDEX tid
* Failed: ALTER TABLE {term_node} ADD PRIMARY KEY (tid, vid)
* ALTER TABLE {term_relation} DROP INDEX tid1
* ALTER TABLE {term_relation} ADD UNIQUE KEY tid1_tid2 (tid1, tid2)
* ALTER TABLE {term_synonym} DROP INDEX name
* ALTER TABLE {term_synonym} ADD INDEX name_tid (name, tid)
* ALTER TABLE {vocabulary} ADD INDEX list (weight, name)
* ALTER TABLE {vocabulary_node_types} DROP PRIMARY KEY
* ALTER TABLE {vocabulary_node_types} ADD PRIMARY KEY (type, vid)
* ALTER TABLE {vocabulary_node_types} ADD INDEX vid (vid)

Whats causing these errors and how do I rectify it ?