opencart upgrade error (urgent help

I have upgraded my opencart from version 11.5.6.4 to 2.0.3.1 and i started getting the following errors when i open www.computersgh.com/admin. please help me with direction how to solve that my website is down, I could not even access computersgh.com/install too

Warning: mysql_connect(): Access denied for user 'computersghuser'@'localhost' (using password: YES) in /home/thompsoncomp/public_html/system/database/mysql.php on line 6

Notice: Error: Could not make a database link using computersghuser@localhost in /home/thompsoncomp/public_html/system/database/mysql.php on line 7

Warning: mysql_select_db() expects parameter 2 to be resource, boolean given in /home/thompsoncomp/public_html/system/database/mysql.php on line 10

Notice: Error: Could not connect to database computersgh in /home/thompsoncomp/public_html/system/database/mysql.php on line 11

Warning: mysql_query() expects parameter 2 to be resource, boolean given in /home/thompsoncomp/public_html/system/database/mysql.php on line 14

Warning: mysql_query() expects parameter 2 to be resource, boolean given in /home/thompsoncomp/public_html/system/database/mysql.php on line 15

Warning: mysql_query() expects parameter 2 to be resource, boolean given in /home/thompsoncomp/public_html/system/database/mysql.php on line 16

Warning: mysql_query() expects parameter 2 to be resource, boolean given in /home/thompsoncomp/public_html/system/database/mysql.php on line 17

Notice: Trying to get property of non-object in /home/thompsoncomp/public_html/admin/index.php on line 43

Warning: Invalid argument supplied for foreach() in /home/thompsoncomp/public_html/admin/index.php on line 43

you have not upgraded your shop, you have replaced it with another Version, not compatible to your existing 1.5.x DB. And probably, without checking here first:
http://www.opencart.com/index.php?route ... ch=upgrade

Ernie
bigmax.ch/os/