If you dont like the shortcuts on your multimedia keyboard jsut because they launch the default programs given by windows then here is a way to change them.
Internet key
Open the Registry Editor and navigate to
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\AppKey\7
Right-click in the right column and create a new String called ShellExecute Set the value as the application path, for example, C:\Program Files\Opera\Opera.exe. If you want to disable the key, delete the value from shell execute and leave it blank.
To change the media player shortcut follow the same procedure with appkey\15