Uncheck to have downloaded archives expanded immediately. (if so defined in InternetConfig.)

Check to have Opera not immediately expand archives. (Nice if you don't have much diskspace, RAM, or just are in a hurry.)

Opera will do this when it encounters a file with this MIME Type/file name extension. Click "Edit" to change.

Click to add a MIME Type entry.

Click to delete the selected MIME Type entry.

Click to make changes to the selected MIME Type.

Decide what to do with files based on their name. (The dumb way - only use if you know what you're doing.)

Decide what to do with files based on information provided by the server. (The right way.)