help!!!!!lost my site

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Warning: main(includes/filenames.php): failed to open stream: No such file or directory in /home/bikes/public_html/store/includes/application_top.php on line 53

Fatal error: main(): Failed opening required 'includes/filenames.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/bikes/public_html/store/includes/application_top.php on line 53

is the warning i get...was having problems with checkout...wouldnt go to pay//so i reuploaded general php under functions and applications_top under includes as both appeared to be corrupt..now i end up with above... for link to site .. http://www.jk-bikeparts.com/

any helpers please..as im a novice