b2 conversion not working

I recently installed WordPress into the same database that I am currently running b2 in. I followed the conversion steps, the first step went fine. On the second step, every action had DATABASE ERROR: beside it, the text on the screen after the second step is as follows:
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First we’re going to add excerpt, post, and password functionality…
Database error: [Duplicate column name ‘post_excerpt’]
ALTER TABLE wp_posts ADD COLUMN post_excerpt text NOT NULL;
Database error: [Duplicate column name ‘post_status’]
ALTER TABLE wp_posts ADD post_status ENUM(‘publish’,’draft’,’private’) NOT NULL, ADD comment_status ENUM(‘open’,’closed’) NOT NULL, ADD ping_status ENUM(‘open’,’closed’) NOT NULL, ADD post_password varchar(20) NOT NULL;
That went well! Now let’s clean up the b2 database structure a bit…
Database error: [Can’t DROP ‘ID’. Check that column/key exists]
ALTER TABLE wp_posts DROP INDEX ID
One down, two to go…
Database error: [Table ‘sarah_b2.wp_settings’ doesn’t exist]
ALTER TABLE wp_settings DROP INDEX ID
So far so good.
Database error: [Can’t DROP ‘post_karma’. Check that column/key exists]
ALTER TABLE wp_posts DROP post_karma
Almost there…
Database error: [Can’t DROP ‘ID’. Check that column/key exists]
ALTER TABLE wp_users DROP INDEX ID
Welcome to the family. Have fun!
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Since it said that all was well at the end, I assumed it had fixed whatever database errors it had found, but when I logged back in to WordPress, my old entries hadn’t been added. What’s going on?