A useful Windows 7 feature is AeroSnap. AeroSnap allows you to maximize windows to exactly half the size of your screen, so that you can basically split your screen in two and then compare or copy things a lot easier.
Split Screen via AeroSnap
1. Step Enable Aero. Aero should be enabled by default on your Windows 7 PC, but sometimes it can be disabled although your PC is capable of running it, then you have to troubleshoot Aero.
2. Step You can either drag a window to the left or right border of your screen or you can use the arrows keys to split your screen.
Windows key + Left arrow = snap window to the left half of your screen
Windows key + Right arrow = snap windows to the right half of your screen
You can switch between the left and right half by using the arrow keys while holding down the Windows key. There are many other useful shortcuts in Windows 7. You can print our list of Windows 7 shortcuts.
Dual-Monitor Split Screen
If you have two or more monitors you can of course split your screen and use two different desktops. AquaSnap, a great tool that improves AeroSnap, supports multiple monitors. So, if you want to split your screen and compare two windows, one on each desktop, you should grab AquaSnap!
Stretch video across two screens
This is not directly related to split-screen, but if you want to stretch a video using multiple screens, read our tutorial here.