How can I record stereo on my laptop (see details) ?

Finally getting around to converting my vinyl collection to MP3 using a patch cable from my stereo system. My Dell Inspiron laptop computer has a built-in Sigma Tel audio adapter with input jack labeled ‘mic.’ After downloading Audacity & making a test recording, I realized that the audio input jack is monophonic only.

Looking for some kind of hardware adapter (USB?) to allow recording true stereo (not just split one track into two). High fidelity / good audio quality is important. Is this possible without replacing the whole computer?