I'm using an app called "Earth Bridge" which links a USB GPS receiver (BU-353 and many others) to Google Earth. Google Earth dispalys latiude and longitude as well as elevation anywhere the mouse points to and it can measure distance between points in various units.
The Earth Bridge app displays the GPS postion on googles images. It optionall keep the display centered on your current location. It will also optionally auto-rotates the display orientation to the direction the GPS is moving.
I use it under XP on a 10" Acer Aspire and a 15" Dell notebook. (under $300 with the GPS for either) Neither have built in CD's keeping them light weight. The 10" display is clear with a magnifier but I have trouble with my WWII vintage eyes.
Google's satellite images and maps of an area can can be downloaded and saved in advance so an Internet link isn't needed in the field. The high resolution satellite images are great because you can easily pick out individual trees and other terrain features as distance reference points. It's slower than using a laser rangefinder but about the same accuracy to idenfiable surface features.
Best of all the Earth Bridge software is available without charge at:
Earth Bridge - Bridge the gap between Google Earth and your GPS receiver.