I found this in a few different places around the 'net - hopefully it's helpful:
Add a Voice Message to an E-Mail Message
Personalize e-mail with a voice message? You can perform this task using the Windows XP Sound Recorder and a microphone. First, open the sound recorder:
- Click Start, click Programs, click Accessories, click Entertainment, and then click Sound Recorder.
- On the File menu, click New.
- To begin recording, click Record, and to stop recording, click Stop.
- Save the .wav file to a folder of your choice.
- Attach the file to an e-mail message.
To record sounds, your computer must be equipped with a microphone. Recorded sounds are saved as waveform (.wav) files.