Internet Explorer 10 in Windows 8, provides one web platform that supports two browsing experiences: the new Internet Explorer in the Windows Metro style UI experience that is optimized for touch devices, and the familiar browsing experience of Internet Explorer for the desktop. By default, in Windows 8, Internet Explorer 10 will open the version which matches your current environment. If you are on the Metro UI, it will open the Metro IE10. If you are working on your Windows 8 desktop, it will open the desktop version of IE10.

It is the the Metro version of IE 10 that is the default browser on Windows 8. But if you want to change the default to IE10 desktop version, you can do it via Internet Options.

Under the Programs tab > Opening Internet Explorer, from the drop down menu, select Always in Internet Explorer on Desktop.

Click Apply/Ok.

Also see Make Internet Explorer 10 in Windows 8, always open links on desktop