hi, I have installed audacity for windows and lame library on my pc and
I have a problem:
when I export a file (waw or mp3) the file does not have the audacity’s icon… is saved in ‘groove’ so I cannot open it with audacity again… the pc ask me for different application but audacity is not allowed 
help me!
Windows assigns icons to file types that it recognises according to “file extension”. The “file extension” is the last few letters of the file name after the final dot. By default, Windows hides the “file extension” for file types that it recognises.
Example. The correct file extension for a WAV file is “.wav”
If a file’s name ends with “.wav” (for example, a file called “AudioRecording1.wav”), Windows will hide the “.wav” so you will see the name as “AudioRecording1” (a stupid decision by Microsoft in my opinion. More information here: https://www.bleepingcomputer.com/tutorials/how-to-show-file-extensions-in-windows/).
By default, Windows associates WAV files with Groove Music (a horrible advert supported audio player), so Windows gives WAV files the Groove Music file extension.
My recommendation would be to install a good audio player (for example “Foobar2000” https://www.foobar2000.org/) and associate file types with the new audio player (I think Foobar2000 has an option to do this during the installation).
In my opinion, it is a bad idea to associate WAV or MP3 files with Audacity. Audacity is an “audio editor”, and although it can play files, it is not intended to be an audio player, and lacks many features that are normally associated with audio players.
More about file type associations here: https://support.microsoft.com/en-gb/help/4028161/windows-10-change-default-programs
It appears that Microsoft now make it difficult to select apps that are not from Microsoft Store as the default application for files. There is a workaround in the first reply here: https://superuser.com/questions/1272956/windows-10-removed-the-option-to-set-this-program-as-default