1) Login as admin>goto my profile> private files 2) Upload atleast two files, one less than 100 kb in size and another more than 100kb in size. 3) Goto any forum click on edit settings under forum administration 4) Change max attachment size to 100 kb and save. 5) try to create a new topic and/or reply to existing topic 6) try to attach files to the post from your private area 7) You should be able to attach the file that has a size <100kb easily and should get an error for the other one. 8) In the later case make sure the file is not present in the post after you close the file picker and make the post.