I've found some info about it. It's not Sandbox but Enhanced Protected Mode
Internet Explorer 10's Enhanced Protected Mode described Internet Explorer 10's Enhanced Protected Mode described
"Earlier this week, Microsoft updated the official Internet Explorer developer blog with an entry on how Internet Explorer 10 has been made to fight off exploits from cyber attackers. But what if a hacker has found a flaw in IE 10 that can be used for malicious purposes? In the newest IE developer blog update, Microsoft's Andy Zeigler writes about how IE 10 can still protect a web surfer's data from such an event.
The new feature is Enhanced Protected Mode, which is basically an evolution from the Protected Mode that was first introduced in 2007 in IE 7 and Windows Vista. Enhanced Protected Mode is designed to keep areas of the operating system out of reach of any exploit that manages to install malware or modify any of your PC's settings."
Internet Explorer 10 gets a new sandbox : Enhanced Protected Mode Internet Explorer 10 gets a new sandbox : Enhanced Protected Mode
"I was told that, in Windows 8, Internet Explorer 10 would be sandboxed in a new way that will greatly improve its security. So much that Microsoft expects Google Chrome to use the same sandbox in the future. However, in the Developer Preview of Windows 8 this sandbox was not yet enabled.
Since the release of Windows 8 Consumer Preview, it is now enabled by default on the Metro version of IE10 (but not on IE10 desktop).
How to enable it on IE10 desktop too"
I still have questions about sandboxed Internet Explorer; therefore, to be continued...