well, i thought about the fact that they used to put 5 or 6 disks on top of one another in server and workstation drives (before better densities were developed) but...idunno...why would they put that on a consumer pc?
The standard symbol to represent a hard disk in the I.T world is a cylinder that, I guess, resembles a can.
That's the reason that a little "can" (or cylinder) is customarily used to represent the hard disk on the face of computer cases. A led (or light emitter of some sort) was added to indicate hard disk activity.
The reason a cylinder was chosen is because each platter of a hard drive is logically divided into concentric tracks. A set of tracks, each on a different platter, at the same distance from the center, forms a logical cylinder. It is from this fact that the cylinder became representative of a DASD (Direct Access Storage Device - formal name) or more commonly called a hard drive or hard disk.
It dates back to shortly after the day IBM invented the Winchester drive (aka Hard Drive). I don't know if the symbol was chosen by IBM at the time (which could very well be) or if it happened later when the drives where made available and the industry as a whole needed a way to represent them schematically.
Either way, the symbol dates back around 50 years by now.