If you are running Windows 10 Technical Preview build 10049, chances are you have used or are using Project Spartan. This is Microsoft's newest browser, which takes advantage of the latest web standards with a new Edge rendering engine.
Project Spartan is a “new web browsing experience for Windows 10” and right now the browser is available for testing on build 10049. For those of you who have been using Spartan on a regular basis, you likely want it to open web pages by default whenever clicking on a web link. When Windows 10 is released this summer, Spartan is expected to be the default web browser. But that's not the case yet.
So how do you make Spartan the default web browser? Very easy! Simply hit the Start button and go to the "Settings" app. Once you are in "Settings", click or tap "System". From there, select "Defaults", then under the "Web browser" category, select Project Spartan. And there you have it, Spartan will now launch as your default web browser.
Keep in mind that Windows 10 Technical Preview is still in developmental stage, so you may expect some compatibility issues as of now and some features or settings might not work as expected. Don't forget to provide Microsoft with feedback too!