Which microphone should I use?

I'm planning on recording some dialogues for language learning. We will be some people around a table with a microphone and a computer with Windows Vista. The dialogues are around 5 or 6 minutes each one. My question is: which mic should I use? Would a Snowball or a Samson C03U be appropriate? When recording with a computer, is sound always processed through Windows sound recorder or is there another software (ex: Audacity) to increase the recording length? Thanks.