It only beeps when I pull the video into the timeline, not when I preview the video in the media pool. Like I said, it will beep every 4 seconds. The media I imported was from a Hi-8 camcorder which I passed through my sony mini-dv camcorder via firewire. Still scratching my head.
Which software are you using - Vegas Movie Studio or something else? What does the beeping sound like - does it sound like one of the Windows-based sounds? Or does it sound like some sort of interference? Just curious. This is a very odd problem...