Normally, you have to boot Windows 8 and when the tiled desktop UI (formerly known as Metro) came up, you had to click on one of the boxes to launch Explorer. Prior builds of Windows 8 allowed the user to create a shortcut so you bypass Metro and go straight to the Explorer desktop.
Rafael Rivera, co-author of the forthcoming Windows 8 Secrets, confirmed to Mary Jo Foley at ZDNet that Microsoft does indeed block the boot bypass routine from prior builds.
He also believes that Microsoft has blocked the ability for administrators to use Group Policy to allow users to bypass the tiled startup screen. There had been hope that Microsoft would at least relent and let corporate users have a bypass, if only for compatibility’s sake.