Virtually any noise removal plugin will do the trick. Generally, it'll take a sample of "silence" where all you here is the crackle, and then it'll take that and use it to remove the crackle from the rest of the recording. I know for a fact that Audacity (free) comes with a good noise removal plug, but if you wanna stick with whatever you've got, well, google is only a step away...
http://www.google.com/search?hl=en&q=noise+removal+plugin&btnG=Google+Search
I am but mad north north-west; when the wind is southerly I know a hawk from a handsaw - Hamlet, Hamlet