Firstly, I suggest you download and install the latest version of Free Download Manager from the official web page.
After that, if you're using Mozilla Firefox, go to Settings > Add-ons > Extensions and disable all other downloading programs.
If you're using Chrome, type chrome://extensions/ in the address bar and disable the plugins.
In Opera, you will need to navigate to Tools > Extensions > Manage Extensions and disable the additional downloading utilities.
If you're using Internet Explorer, press the Alt key and from the Tools menu select Manage Add-ons. Locate all additional downloading programs and disable them.
Note: In all browsers you will need to make sure that Free Download Manager is enabled.