The plugin does not alter any WordPress files. I don't know why WordPress is still trying to call it if you'd properly installed it, but the easiest way to completely remove it is to simply delete all of the plugin's files. You might also have made some call to it in your template, or you might have a caching plugin that is still trying to load it.

I've disabled this plugin but it's now throwing database errors.

[10-Oct-2009 16:54:03] PHP Fatal error: Call to undefined function add_action() in /blog/wp-content/plugins/random-anti-spam/random_anti_spam.php on line 437

[10-Oct-2009 18:09:52] WordPress database error Table '*******.wp_ras_image' doesn't exist for query SELECT word FROM wp_ras_image WHERE id = 21675

Can you tell me what wordpress files this plugin has altered so I can find out where this is still be called.