Assuming that :- 1. The recording is a close match to your voice 2. Your ear does not significantly filter airbourne sound 3. The ear of your friend doesn't significantly filter airbourne sound Then:- Play the recorded sound through a filter. Adjust the filter parameters until you perceive the recording to be identical to when you spoke it. Your friend will then hear it the same as you do. Free audio lab software will let you experiment with filters, for example http://www.nch.com.au/wavepad/index.html
It should be a NCH WavePad file, assuming it's audio at all.
Try following this tutorial to convert it using audacity, in case it has any steps different from what you have already tried. If that doesn't work I don't know what to tell you except to ask whoever made it to export to a more compatible format. Or you could see if there is a limited time trial of WavePad.
Hello, NCH Software has some great software for editing audio and video. We also have helpful tutorials to get you started. For video editing, check out VideoPad here: http://www.nchsoftware.com/videopad/index.html For editing audio, check out WavePad here: http://www.nch.com.au/wavepad/index.html
By today's standard's that system is grossly underpowered, but that's only relevant if you intend to run an up-to-date version of the OSX operating system. If the software is every bit as old as the hardware, it won't matter as much. (EDIT: Sounds like this is a moot point, but posting anyways for my second point)
Also, I personally think Audacity on OSX is terrible. It's free, yes, but so much more is available for reasonable amounts. Top of my list is Adobe Audition (also the most expensive, but IMHO worth every penny if you buy it outright, rather than subscribe via Creative Cloud), but if you want to keep the budget tight, look into WavePad by NCH Software. If you don't need VST support, it's only $35.
In any case; congrats to you for pursuing a fun hobby (and so much more). GET AFTER IT, and welcome to doing VO!
Cheers...