I had various issues with crackling and static when I was using my laptop for production. It seems ok now as I've done lots to it:

- delete files to free up memory
-don't have too many programs on at once
-unplug all non essential USB devices and pluginswhen recording/playing back (eg wireless mouse and PCMCIA card)
-change the power options, as power saving modes can affect sound recording and playback
-regularly update drivers, especially soundcard drivers (if you have them)