Having spent more than a decade as a bridge between the general public and technology, this is a misconception that I have experienced quite a few times.
A hard drive is not a computer; rather, it is an integral component of a computer's operation.
A computer is a complex machine, comprised of multiple interrelated devices.
The processor, or CPU, is the brain of the machine, responsible for performing billions of instructions in the blink of an eye.
RAM is the computer's short term memory, which enables the processor to spend more time executing code rather than learning what to do next.
The processor is at its fastest when it is working, so it's in any PC's best interest to have as much RAM as possible so that the CPU can focus on what's important.
Being a short term application, if the computer is turned off, the contents of RAM vanish.
Your keyboard and mouse are tools that you can use to talk to your computer, and the monitor and your speaker system are the tools that your computer uses to talk back.
The computer case is the big metal box that people commonly refer to as a computer (or 'hard drive', hence this article!) - in the olden days as it lay horizontal and flat on the desk, computers picked up the nickname 'desktop'.
Manufacturers got smart in later years, designing the case to stand vertically and allowing the 'tower' to go in more convenient places, such as inside a desk or cabinet.
The actual hard drive is the computer's long term memory.
All of its programs and installed code reside on it, and are pulled piece by piece into RAM, awaiting the CPU's attention.
The hard drive itself is a very small box, big enough to fit inside the palm of your hand.
Hard drives are typically installed inside the case, but as of late they can be found plugged in via cable (ie: USB) in an external fashion.
CD/DVD drives (and the old, antiquated floppy!) are other types of long term memory.
The big draw back is in the security and integrity of your information: they can be easily lost, stolen or damaged.
Optical media such as these also suffer the drawback that they are incredibly slower for the CPU to read, and they are enormously inferior to hard drives in terms of size.
So now that you know the name and function of the major components of your computer, you are one more step towards 'computer literacy'.
The next time you point at your tower/desktop/pc, call it proudly by its proper name, 'computer', and not 'hard drive'.
If you ever have any question about PCs but have been afraid to ask, shoot me an email.
Daniel