Hello swimnub Welcome to the SevenForums!
Actually you are under the wrong impression about any larger gap between the recovery partition and C. When you have a 160gb drive but see a 7.06gb recovery and 141.99gb OS primary you wonder where the other 6gb went I assume.
What's missing? The conversion of units of measurement by how drives are sold to how they are measured by Windows or any other OS. Drives are sold by the decimal "units of measurement" while an OS sees a drive with binary "units of measurement". To avoid confusion a good article published back in 2007 also includes a calculator to see the difference when converting from decimal to binary. The Tomorrow Times: The Hard Drive Capacity Calculator