Something I’ve often wondered about: why is a 20 gigabyte hard-drive actually only 18.6 GB? Some folk in LA are not only wondering, they’re suing. The Register reports that US PC users have banded together to protest against “deceptive advertising” of hard drive capacity by filling a lawsuit against the world’s biggest computer manufacturers. The lawsuit objects to the notation used in describing the capacity of hard disk drives in manufacturers’ promotional material. For example, a “20 GB” hard drive would only have 18.6 GB usable capacity, the complaint maintains.