How can I make the converted audio files stay in the same folder?

If you want your converted files to end up in the same folder as the original files, go into Audio Converter Pro's options and change the "Converted Audio Files Directory" setting to a single period, like this "." (without the quotation marks, of course).

To access options, click on the Windows Start menu, then Programs, then Acoustica Audio Converter Pro and then Options.

This trick will work for MP3 to Wave Converter PLUS as well.