How to manually delete a post?

I’m having problem with my database…all of a sudden, am using WP 2.1.2

Fatal error: Allowed memory size of 25165824 bytes exhausted (tried to allocate 1442484 bytes) in /home/MyUserName/public_html/wp-includes/wp-db.php on line 161

Now the post has turned protected, and I cant even delete it. How do I delete the post from the mysql manually, as in the files to delete? Where should I look in the database?

Thanks