(using the full package)
If you have Protector previously installed, open the "mainfile.php" file , and remove the Pre-check and Post-check lines (if they exist):
include XOOPS_TRUST_PATH.'/modules/protector/include/precheck.inc.php' ;
include XOOPS_TRUST_PATH.'/modules/protector/include/postcheck.inc.php' ;
For security considerations, you are encouraged to move directories xoops_lib (for XOOPS libraries) and xoops_data (for XOOPS data) out of document root, or even change the folder names.