I'm very sorry for the loss of your husband. But, it's wonderful that you have his voice on your phone. Don't ever delete it! I'm sure that it is a comfort to hear his voice.
My brother passed away unexpectedly a few years ago. I don't know why, but I called his phone and heard his voice mail away message and felt some closure after listening.
I wanted to record it and not lose it.
I have a little Tape Recorder that I bought at Radio Shack. I also have a Telephone Microphone Pickup that attaches to the phone. The mic. has a suction cup that I placed on the back of the upper Flip portion of my phone. It recorded the message perfectly.
Now I have it on a little tape cassette that can't be erased.
I never thought of putting it on the PC, but I'm sure you would do the same thing. Just plug the mic. into the mic. socket on the PC and record it.
I wish you success.
Sorry for your lost...
What you might be able to do is go to Radio Shack, and get a 3.5mm audio cable, plug that into the phone, and plug the other end to your computers recorder port (the red one) and record the the voice by using windows voice recorder, that might work... basically instead of a mic, it woul be recording whatever is playing.