The Apple QuickTime player:
you cannot live without it - and on Windows not with it! An often complained problem is,
that the player-installation hijacks associations of file-types and mime-types.
The original settings can only be restored with some tricks:
Firefox 22 and later:
The browser uses the built-in media-playback. To use the codecs of the operating system for playback
of MP3, MPEG and HTML5 videos the browser-configuration can be changed as following:
Start Firefox
In the adressbar enter about:config
and confirm with the "Enter"-key.
Confirm the displayed warning (if shown).
Look for the entry named media.windows-media-foundation.enabled
and double-click it to change the value to false
Restart Firefox
Firefox 21 and earlier:
In general its recommended to update an earlier version. If not possible:
Start Firefox
If the menu is not shown: press the F10 key
Extras -> Add-ons (Ctrl+Shift+A)
Plugins
Select "QuickTime Plug-in", "Never Activate"
Internet Explorer:
The procedure is a little bit more complicated:
First open the Explorer (key "Windows"+"E") to figure out
in which folder Apple QuickTime is installed
e.g. "C:\Program Files\QuickTime" or "C:\Program Files (x86)\QuickTime"
Open "Command Prompt" as Administrator.
Windows 7 and later: open the "Start"-menu by pressing the "Windows" key, enter CMD
to search for "Command Prompt", right-click the found entry to open the menu and select "Run as administrator".
Confirm the message displayed by windows (if any)
In the Command Prompt window switch to the Quicktime directory: C: (respectively remembered drive, then hit "Enter"-key) CD C:\Program Files\QuickTime (respectively remembered path, then hit "Enter"-key)