Simple way to get Start Screen of Windows 8 in Windows 7 is explained in simple steps here
steps to follow::
1.Download the Rainmeter Software and install it.
2.Using Rainmeter download a skin, say Omnimo 4.1
3. Install the Downloaded skin
4.After skin installation, run rainmeter and you get the tile based view.
then just customize the start screen as users wish
Now you can enjoy Windows 7 with Start Screen of Windows 8
[ simple description to Get Windows 8 Start Screen in Windows 7 from Pigotechguru]