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 and onwards require .NET 4.0 (released in 2010). Windows 7 is guaranteed .NET 3.5, so may require an upgrade. (Windows XP can run .NET 4.0 with service pack 3).

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

• Cross your fingers.
• 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.
• 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).
• 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. Setup.exe checks if you have the necessary .NET version on your computer (this is usually the case, but if not so your .NET version will be upgraded automatically), and then afterwards calls the InstallerForGekko.msi file.

(NOTE: If all this fails, you may try to manually upgrade your .NET version to at least version 4.0, 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. In severe cases, burning the InstallerForGekko.msi file to a CD and installing from the CD might also be an option to try out).