Apple's iTunes software allows users to encode the files in their libraries into a variety of formats and qualities for compatibility or disc space purposes. Use the encoder to create duplicate versions of your iTunes files, should the need arise.
Check the format and the bit rate of the file you want to duplicate by clicking on the file in your iTunes library, selecting the "File" menu and choosing "Get Info." Note the "Kind" and "Bit Rate" fields.
Set your iTunes encoder to this file format and bit rate in the iTunes preferences panel. Access the panel by selecting "Edit," "Preferences" ("iTunes," "Preferences" on a Mac) from the menu bar. Click the "General" tab if it's not already highlighted, and select "Import Settings." Click the "Import Using" menu and select the same format as was listed in the "Kind" field in Step 1. Set the "Setting" menu to the same bit rate as was listed in Step 1. Click "OK."
Open the "Advanced" menu from the top of your screen. Select the "Create [your file format] Version" option. ITunes creates a duplicate copy of the file you selected, listed just below the original in your library.