To convert mp3 files to wav format using Winamp 5.55, all you have to do is to configure the program to modify the audio output, follow these steps:
Click on the Options menu> Preferences
In the window that opens, select "Plug-ins" > "Output"
In the right pane, select "Nullsfot Disk Recorder v2.14 ..." (In this mode you can not hear audio files). Then click on "Configure"
In the "Conversion", check "Convert to format". If you want to change the output file location, click the button to the next "Directory" > choose the folder of your choice and click on the "OK" button
Now open the mp3 file you want to convert with Winamp and the conversion will start automatically.
After the conversion, you must reconfigure Winamp so you can play the files normally. To do this: Options> *Preferences> Output (Plug-ins)> select Nullsoft DirectSound Output ...> click on the Close button "