Maybe try this winamp plugin:
http://www.chronotron.com "Chronotron Pro is a professional audio plug-in that allows you to manipulate tempo and pitch separately, that is, it allows you to change the tempo of a sound track without affecting its pitch (time stretching) as well as changing the pitch without affecting the tempo (key change).
The plug-in can be hosted on any DirectX plug-in host application (like Sony Sound Forge or Steinberg WaveLab) to permanently change the tempo and key of your audio material.
You can also use Chronotron Pro directly on Windows Media Player 9.x or later during playback of most types of media, including video files.
Chronotron was the first plug-in to deliver high quality audio in real time at reasonable scaling ratios. Chronotron Pro uses a re-engineered version of the algorithm featuring superior performance, wider effect range (from 25% to 400%!) and improved sound quality.
When hosted on Windows Media Player, a loop function allows for easier music transcription."