|Almost any computer will do. Sound recording, unlike video, is not very demanding on computer resources. An old 1 Ghz CPU would be more than adequate.|
The most critical factor with sound recording is the sound card and the software you are using. A good quality sound card will be adequate if all you are recording is voice. You need really high quality and ridiculous high prices when music is involved.
The same goes for software and Audacity is as good as you are going to get without again getting into ridiculous high prices aimed at professional music production.
Of course a good quality mic is important. It wont matter one jot if you have a high quality sound card, Audacity and a crap microphone.