Backing up only comments, posts, and related data

I am trying to move my stuff from stupidcomplexities.com to janicelo.com/blog (to a new host as well), I first tried with backupmyblog’s restore function, but it turned out the hyperlinks are all pointing back to my old domain. Then I followed faq.wordpress.net’s guide to backup and restore, and I came up with an error screen saying:

SQL query:
-- --------------------------------------------------------
--
-- Table structure for table wp_categories
--
CREATE TABLE wp_categories (
cat_ID bigint( 20 ) NOT NULL AUTO_INCREMENT ,
cat_name varchar( 55 ) NOT NULL default '',
category_nicename varchar( 200 ) NOT NULL default '',
category_description longtext NOT NULL ,
category_parent bigint( 20 ) NOT NULL default '0',
category_count bigint( 20 ) NOT NULL default '0',
PRIMARY KEY ( cat_ID ) ,
KEY category_nicename ( category_nicename )
) ENGINE = MYISAM DEFAULT CHARSET = latin1 AUTO_INCREMENT =44;
MySQL said:
#1050 - Table 'wp_categories' already exists

—-

Should I not install wordpress before restoring? Or is there any method I can only backup and restore comments, posts, and other related data, such as wordpress categories?

PS my previous domain is running 2p 2.0.3, but I have already upgraded it to 2.0.5 before backup, so I pressume that we can rule out the failure due to a 2.0.3 to 2.0.5 restoration.

Many thanks!!!