It is most convenient to limit the downloading files in Opera browser. To do this, open: "Tools" - "General settings" - "Advanced" - "Contents" - "Blocked content" and add the file extensions you want to block. For example, *.. exe for executable files, *.avi for video files etc. All files with the specified extensions will be blocked when you try to download them.
To prevent downloading files in Internet Explorer, open "Tools" - "Internet options" - "Security". In the window "Select a zone to view or change the parameters of its security", select "Internet" and click "Other..." In the window "security Settings - Internet zone" to find "list Settings", and in it group Download. In this group for the option "file Download", select "Disable" and save changes by clicking OK.
There is a possibility to establish a ban on the downloading of files directly in the system registry. To do this, type regedit on the command line, then in the window that started the editor, open the registry branch: HKEY_CURRENT_USER \Software \Microsoft \Windows \CurrentVersion \Internet Settings \Zones \3.
In the right part of the window, find the line "1803", click right-click and select the context menu item "Edit". Opens a small window where you can change the parameter value from 0 to 3. Save the changes. After this IE can't download any files from the Internet. This method is quite radical, but in some cases it may be useful.
If the computer employs a few people and need to control their traffic, including file downloads, are best installed on computer, proxy server with access to the Internet by login and password. In the settings of the proxy server you will be able to prescribe the rules and ban the downloading of certain files.