My Macbook is also making clicking noises.

Recently my two-year old MacBook, which is running on OS 10.3.9, has started making clicking noises. Does anybody have any idea as to what the cause or origin of these noises might be? The noises do not seem (in any intuitively obvious way) to emanate from the hardware itself. They sound more like a digital reproduction/projection of the sound of typewriter keys. They also sound like they come from the same place (so to speak) as the sound you hear when you throw something in the trash or place an electronic document in a folder.