As far as I am concerned a 20gB drive holds 20gB of data. Some of that data is invisible to the user as it is actually formatting data the OS uses. A certain amount of drive capacity has always been lost to formatting. It has always been so and always will be.

If you perform the calculations using the number of heads, cylinders, tracks, sectors you can calculate the actual capacity of a drive in bytes. When was the last time anyone actually saw how many heads, etc their new drive has?

Stuart