Recording off of the aux port to my computer

[chiptransisto]

Partner acs v6, voicemail card 2 ports.
I want to save some voicemail messages to my computer in mp3 format. I tried to use an adapter from Radio Shack that plugs into an analog phone outlet and records phone calls. When I plugged it into the aux port on my partner system, I can hear myself clearly but the other person's volume or the voicemail message volume is so low that it is not useful. I have adjusted all of the sound volume controls on my computer but it still doesn't work. I can hear the other person or voice message clearly but the sound does not make it to the computer.
What is the best way to record a voicemail message to my computer?

 

[tgadd]

You might want to try an adapter that goes throught the handset cord.I know there are some suppliers of recor-a-call adapters that you could probably use the mic out for your computer.