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First of all, you may safely ignore Windows security warnings similar to these:

Warning pop-up
Warning pop-up

Regarding the latter, press ‘More info’ to run the installer anyway.

Apart from such warnings, if installation is problematic, for instance if an old version keeps showing up even if you have installed a newer version (or the installation fails), you may try the following very clean way to do it.

It should be noted that Gekko uses standard Windows components, so on a Windows pc (or on a Windows version hosted virtually on e.g. a Mac), Gekko should install and run without a hitch. Gekko versions 1.8, 2.0, 3.0 and onwards require .NET 4.0 (released in 2010). Windows 7 is only guaranteed to contain .NET 3.5, so it may require an upgrade. (Windows XP can run .NET 4.0 with service pack 3). The development versions 3.1.9 and upwards require .NET 4.6.1 (released in 2015) to run.

The procedure below should make sure the right .NET version is installed automatically on your computer, if needed.

  • (1). Cross your fingers.
  • (2). Close any open Gekko version. Then un-install all traces of Gekko manually (Control panel –> Programs and features –> Uninstall a program). If there are several instances of Gekko on the list, remove all these instances one after another.
  • (3). Create a new folder, for instance a sub-folder to your desktop folder. The folder should have full read and write permissions, and the folder should not be encrypted (to check this, right-click the folder in Windows Explorer, choose “Properties”, and click the “Advanced” button).
  • (4). Save both the installer (InstallerForGekko.msi) and the setup.exe file into the newly-created folder (right-click the two links one at a time and choose “Save destination as….” or “Save link as…”). IMPORTANT: Make sure the two files are called “InstallerForGekko.msi” and “setup.exe”, if not so: rename them. Sometimes when downloading, a version number may be added to the file, for instance “InstallerForGekko (4).msi” — so remove such a number, including the blank before the number.

In the newly-created folder, double-click setup.exe. InstallerForGekko.msi is the “real” installation file, but setup.exe checks if you have the necessary .NET version on your computer (and if not so, your .NET version will be upgraded automatically). Afterwards, setup.exe should call InstallerForGekko.msi file automatically.

A few users have had the problem that the installer (setup.exe or InstallerForGekko.msi) keep saying that a really old .NET version is needed (something like .NET 2.0), but fails installing this, and then refuses to install Gekko. The source of this problem is not known. A work-around regarding this problem is to “install” manually from a zip file ( Just unzip the files, put them in a folder somewhere on your computer (for instance in a folder called “Gekko”: the folder does not need to be under C:\Program Files\…), and double-click gekko.exe. After this, Gekko hopefully starts up, and the only thing missing is that Gekko will not be present in the Windows start menu (this can be remedied manually with a file shortcut link). The .zip-version of Gekko is just as good as the .msi version, and many users actually prefer using the zip version.

NOTE: If all this fails, you may try to manually upgrade your .NET version to at least version 4.0 or 4.6.1, and then afterwards try to copy the InstallerForGekko.msi file to a USB stick and run the installation from there. This has helped at least one user running Windows XP.

Some cases have been reported where the Gekko window is not visible, although the Gekko icon can be seen in the Windows taskbar (and there is an active Gekko process running). This is usually because the Gekko window has been placed outside of the current window (for instance on an extra monitor that is no longer attached). Gekko remembers window positions, and it is in principle possible to delete or change a Gekko user.config file containing this info (but difficult in practice to obtain the location of this file if the Gekko main window does not even open…). On Windows 10 it is easier to Shift + right-click on the Gekko icon in the Windows taskbar. After this, you may move or maximize the Gekko window (in Windows 7 this is done a bit differently, but the idea is the same).

Mac/Linux users, see here.