Empty Space

Was wondering why I have this empty space at the bottom of my tools. It is always there even when I turn off those bottom rows of options.

I see the same space on the right side of your sidebar menu.
This could be a Windows text and icon sizing thing or a video driver thing.
Have your messed with the Windows text and icon sizing?
What graphics card and driver are you running?

That gap in the left hand column is where I have my viewport tabs. I may have altered my Windows system font a bit, not sure. The font and size of those tools are controlled by Rhino Preferences.