input levels of audacity

I am using an IBM T41 Thinkpad laptop with Windows XP and a phono pre-amp for recording LPs which I then make into WAV files and put on CDs. As the Thinkpad does not have an audio interface beyond the mic-in, I got a special Docking Port which has a line in connection. This system works but there are a number of curious features which I hope you can shed light on.

  1. The recording Input levels are substantial even when there is no signal input.
  2. The two channels are not matched. The left channel shows a higher reading than the right channel, even when there is no signal input (even when nothing is plugged in but the record button is depressed).
  3. Does this indicate that I need an external sound card?
  4. Is the Behringer UCA202 an external sound card? (It is listed as an audio interface and not as a sound card, but many also refer to it as a sound card.)

I’ve never used a Thinkpad Docking Port, but from your description it sounds like the line input is very poor.
The UCA 202 should perhaps be more accurately be described as an external audio interface and the term “sound card” used for circuit boards that provide an audio interface and plug into full size computers. In practice the terms often get used interchangeably for any electronic device that provides input and output audio connections for a computer.