ok, here is what HDD companies use:
300,000,000,000
/1000
/1000
/1000
=300GB
Here is what your computer gives you:
300,000,000,000
/1024
/1024
/1024
=279GB
There is nothing you can do about it. There is already a lawsuit out there, but it is going no where because the top numbers are correct. The correct terminology for the base-2 equivalent of 2^30 is Gibibyte, or 1 GiB, not Gigabyte.
If you want to analyze a particular drive, give me the model or a link to its ad and we can check the terminology they use closer...
Vaughn