How to copy virtual devices downloaded by Genymotion to another machine?

The files in the VirtualBox folder are likely just the actual machine configurations, not the downloaded image files.

On my system (Windows 8 x64) the downloaded images are located here:

\Users\{username}\AppData\Local\Genymobile\

Inside this folder is another folder called LaunchPad. If you copy this folder to the same location on your other machine it should work.

I would advise you install and run Genymobile on the other machine, then exit it and copy the folder mentioned above. Re-launching it should then pickup the image files.

You will have to re-create the actual devices, but you won't have to download the images again.

I have also noticed that you only need to download 4 images - any tablet with/without google apps and any phone with/without google apps. All the different phones/tablets use the same physical images once they are downloaded.

UPDATE (for Genymotion v1.1.0):
The folder for has changed in v1.1.0 - it is now called Genymotion instead of LaunchPad, but it is still in the path indicated above. In order to retain already downloaded images (from v1.0), rename the LaunchPad folder to Genymotion (or copy it's contents if it already exists).

Update for Genymotion v2.0+:
The folder is now called Genymotion (instead of Launchpad) but it's contents remain the same, just copy it to your other installations.

Additionally, images with Google Apps are no longer available - so you only need to download 2 images per version (phone/tablet). To get Google Apps in Genymotion there is a solution posted on XDA.

Update for Genymotion v2.8+: The downloaded images are located at:

\Users\{username}\AppData\Local\Genymobile\Genymotion\ova

The answer marked as correct is no longer valid for GenyMotion 2.2.0 (at the time I didn't have high enough reputation to comment so I added this answer instead).

Testing with GenyMotion 2.2.0 the image files are now downloaded into:

C:\Users\ {username}\AppData\Local\Genymobile\Genymotion\ova

To re-use the downloaded images on a another machine without downloading them again:

1. Copy the desired image file(s) to the ova folder on the second machine.
2. Restart GenyMotion.
3. Create a new device matching the version of the image you copied over.
4. GenyMotion will warn that the new version will be downloaded.
5. Click next (don't tick the option to use cached files).
6. GenyMotion should create the new device without downloading the image.

Update - potential problems:

Version of Genymotion and the virtual device are different:

If you receive this error message:

1. Open VirtualBox
2. Right-click your Genymotion virtual device and select Settings
3. Select the System section
4. Check that the Acceleration tab is not dimmed and that the VT-x/AMD-v and Nested Paging options are enabled
5. If not: try enabling virtualization in your PC's BIOS.

Thanks to Ahmed Nazmy who found the problem and posted a solution in the comments!