help: 用 Sound Card 的 Line In 來錄製 MP3

[wcm888]

I want to convert the 錄音帶 to MP3, and I have prepair the following tools:
1. a cable between the Walkman and the Sound Card (Line In)
2. recorder software (I have tried the Goldware, Cool Edit, NeroMix and Totoal Recorder)

the problem is:
1. 當嘗試用 Walkman 來播放時沒有問題.
2. 當錄製時, 一邊錄一邊聽時都沒有問題,
3. 但當我想播放剛錄製好的 MP3 時, 噪音相當大, 根本聽不到內容 , 有很多雜音.
4. 之後再用MD來試, 但結果都一樣.

我已清潔了 line In o果窿.

求各方友好賜教, 因為我已經試了很久. 謝謝.