MyBB Community Forums

guys i own a forum.i am facing a problem i;e whenever i click on any forum it redirect to

http://xxxxxxx.net/forum-x.html

and the same home page opens.but when i open

http://xxxxxxxx.net/forumdisplay.php?fid=7 

it opens normally.so can anyone tell me how to change the url form

forum-x.html to forumdisplay.php?fid=x

thanks in advance

admin panel --> configuration --> settings --> Server and Optimization Options -->
Enable search engine friendly URLs? <-- select Automatic Detection OR Disabled

Also, rename .htaccess to htaccess.txt