The recording worked but there is much background noise - any suggestions ?
Check your recording options and try setting them to CD quality (44,100 Hz). That may help.
There are also several freeware and shareware wave editors (such as Goldwave) that have hiss/pop and other filters/functions. Hope that helps.
If you are using a software synthesizer, it is not uncommon to get very poor results. If this is the case, refer to your synthesizer docs for details.
In any case, you may get better results recording your sound card output to tape, then digitizing your taped output sent to the line level input of your card.