Please note that there are 2 main lines:
2.9.6 is the latest in the line for php4
3+ versions are for php5

And both should be downloaded from the link on my signature rather than the download section.

If you remove it, make sure you revert .htaccess back to normal.
Then you need to remove any changes/any new files uploaded during the installation

Then in admin->tools->sql patch runs:

PHP Code:
SET @t4=0;
SELECT (@t4:=configuration_group_id) as t4 
FROM configuration_group
WHERE configuration_group_title
'Simple SEO URL';
DELETE FROM configuration WHERE configuration_group_id = @t4;
DELETE FROM configuration_group WHERE configuration_group_id = @t4