Who told you the recording cannot be edited in Captivate? Of
course it can, though the audio editor in Captivate is definitely
not a full-featured tool.
But I think your problem might be in the recording itself.
Make sure you have a good *sound environment* in which to record.
And make sure that you have a decent (not expensive, just solid)
audio card for your PC. And finally, get a decent quality (again,
not expensive, but solid) microphone.
That aside, the answer to your question is that there are a
huge variety of audio editors out there to select from, including
the freely available *Audacity*, and Adobes Systems *Sound Booth*.
The trick to cleaning up existing problems like hissing is to (in
effect) drive up the volume on the waveform, so that the hissing is
less noticable as a component of the waveform. In some cases, it is
just not possible. That is why *digitally remastered* old songs are
often still crappy when listened to.
You can Goggle for *audio editor* to get info on other
editors. Good luck.