Need advice on best way to handle downloads

I have a client who records 10 minute mp3 files that she sells on her zencart store. The size is fairly large. I did not want it to be a burden to the customer to download so I zipped it into an executable file.

I have been working in PC's all my life and did not realize that EXE files were strictly PC so the first time a MAC user purchased the item it obviously would not open.

I am not sure what the best way to handle large file downloads that will work with both the MAC and the PC environment. The customers are not computer savvy and may not have a unzip program already loaded on their machine.

What has everyones experience been with this and what are your suggestions to make this work successfully.

Thanks in advance