songdogtech on "Internal Server Error 500"

Also, delete the old plugin tables from the database as a whole; that can make a big difference. The standard WP tables are

wp_commentmeta
wp_comments
wp_links
wp_options
wp_postmeta
wp_posts
wp_terms
wp_term_relationships
wp_terms
wp_term_taxonomy
wp_usermeta
wp_users

The wp_ table prefix may have been changed or added to, but that doesn't matter much in this context.