To correctly ENable seo4smf you need to enhance your .htaccess as - well if you unpack your seo4smf package locally - can be seen in the readme file.
However if you enabled it and want to switch it off again, you will need to look up your <prefix>_settings table (presumably smf_settings) and find the variables that start with seo4smf. You should get the idea then

Regards,
Jerry