MEmu is a free Chinese application which runs Android in a window on your Windows desktop.
The main download is horribly slow, so we've linked to the main MEmu page, instead. This has more options, including a Google Drive download which is faster.
Once the download and setup is out of the way, life gets much easier. A window opens representing an Android tablet, a few basic apps - including ES File Explorer - and Google Play Store to help you find and add more.
A right-hand toolbar simulates shaking your virtual tablet, rotating it, adjusting volume, taking a screenshot, remapping keys or running an apk directly, while you can simulate multi-touch and tilting with the keyboard or a joystick.
The Settings dialog includes a "GPS Simulation" tab to define your location. It's set to China by default, so if you're elsewhere you should probably update it.
There are other settings to define the RAM allocated to the process, the number of CPUs, and the screen resolution (although you can run Android full-screen whenever you like).
MEmu also has shared folders for music, videos, pictures and download, making it easy to share content between Android and the host.
Add support to 32-bit Android Lollipop 5.1 (download in Multi-MEMU)
Add support to change WIFI name, DNS server and MAC address
Add support to enable LOL mode for more MOBA games
Improve the compatibility check of VT conflict