Here's how we turn it back
1. Right Click on My Computer -> Properties -> Advanced System Settings -> Visual Effects
tick " Enable Peek"
2. In Windows 8 , right click the very right hand bottom corner of your screen and click on "Peek at Desktop"
3. Aero Peek will only work with Windows Aero Theme's not Windows Basic Theme's. These theme's allow transparent taskbars which is required by aero peek.
4. Right click Taskbar and goto properties. Tick Peek Preview
One last one , if all else fails change the value of DesktopLivePreviewHoverTime from 0 to 500 through regedit -> HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced.