Hey, don't be so fast to write off this possibility.
When I first got a PC, it was a used one that had a Quantum HD with a model number that said it had a 2.1GB capacity... but only 1.2GB was available for use, according to the Sharpie'd numbers on the top, as well as Device Manager. Even when I reformatted and partitioned it to reinstall Win95, all that would show up is 1.2GB.