How to Edit a Song's Length in Windows Media Player
As of 2010, Windows Media Player does not have the capability to edit audio files. To edit your audio files using Windows Media Player you need to download a plug-in that allows the trimming of Windows Media files.
Downloading a plug-in
As of November 2010, the only plug-in for Windows Media Player that allows you to edit the length of audio files available was the SolveigMM Windows Media Player Plug-in. It is a good idea to carry out a thorough Internet search to check for available alternative plug-ins before downloading the SolveigMM version.
Using the plug-in
Once the plug-in is installed it needs to be enabled. This can be done by clicking on Tools/Plug-ins/SolveigMM WMP Trimmer Plug-in or, if the main menu is not visible, by clicking on Now Playing/Plug-ins/SolveigMM WMP Trimmer Plug-in. Once enabled, it is possible to open audio files using the plug-in and trim them using the Trimmer tool bar. This is essentially a cut and paste process whereby it is possible to select the section of the file you want to cut out and save it as a separate file. This does not affect the original audio file.
The alternative to using a plug-in to edit files within Windows Media Player is to download or purchase a standalone audio editing program. You will find many freeware and private options available including Audacity, Goldwave, WavePad (which are free in some versions) or the Magix Music Maker.