Microsoft has introduced preview version of Windows 8.1 for public and it comes with lots of new features, one of them is Boot Directly to Desktop, In Windows 8 when you boot computer or start, it first shows Start Screen and then you can go to Desktop, but in Windows 8.1 Microsoft has added one option which allows you to boot directly to your Desktop and skip Start Screen.
For this you need to :-
Right click on taskbar and select Properties
Now you will see Taskbar and Navigation properties window.
Click on “Navigation” tab and check option “Go to the desktop instead of Start when I sign in”
That’s it you are done, on next boot you wont see your Start Screen