Google Earth Pro is the high-end version of Google's amazing mapping and exploration tool, once priced at an eye-watering $399 a year but now available for free.
Advanced extras include the ability to measure 3D buildings, print higher resolution images or save them as PDFs, or use a Movie Maker tool to record HD video animations of your tours around the world.
You will still need to get a licence before you can install the program by filling in this form. (The URL refers to a free trial, but that's a leftover, it really is free. And while the registration form asks for your phone number, it doesn't appear to care if you enter a single digit, instead.)
Once that's out of the way, download and run the small setup program, and it'll download and install the full Google Earth Pro.
We installed the program alongside a regular Google Earth build and had no problems. We launched Google Earth Pro and it picked up our current "My Places". Close the Pro build and we were able to launch regular Google Earth, as normal.
The only minor issue is that we couldn't run the standard and Pro builds at the same time, but that's much as we expected, and otherwise the dual installation caused us no problems at all.