RTFM:
Open options file with some plain text editor on your computer. Edit your php files with a quality text editor! We recommend Metapad, or simply Notepad, because these editors are not storing additional newlines, spaces or breaks before <?php and/or after ?>. It is forbidden, to have such kind of characters outside PHP execution code, because this may cause problems with your board (for example, you will be unable to log in, and kind of this error appears: Cannot modify header information - headers already sent by (output started at...) | 
