For your first question:
The code will work with IE because it plays the file using WMPlayer.
In Mozilla or firefox it requires the quicktime plugin to play the file.
When you open the file for the first time, I think it asks you
1. Download to disk
2. Open using default application etc
If you choose the default application option it will open either winamp or WMPlayer and plays the file.
Check this out:
http://www.webmasterworld.com/forum21/11810.htm
For your second question there are two options.
It will not be good for you to break the file into many files and play the different files.
1. Give an option for the user to decide whether he want to listen it downright.
2. The user is ready to download the compressed file (compressed using winzip). The user requires winzip.