Enterprise Tester version 6.1 and above requires version 4.6 of the .Net Framework to be installed.
Web Downloader: https://www.microsoft.com/en-us/download/details.aspx?id=48130
Enterprise Tester versions 4.9 to 6.0 requires version 4.5 of the .Net Framework to be installed.
Web Downloader: http://www.microsoft.com/en-us/download/details.aspx?id=30653
If you are using the Enterprise Tester Installer (.exe), the installer will attempt to download and install the .Net framework for you (internet access is required).
If you are using the Bin Zip File to manually upgrade or install Enterprise Tester, then you must manually install the relevant .Net Framework in advance.
When installing the .Net Framework you have two options - either installing from a "web download" (a small download, which will then install only the components you require) or you can download a redistributable file, which is a large file containing all the files necessary for the .Net Framework to be installed on any machine.
If you plan on installing the Framework on more than one machine within your organization it is suggested that you use the redistributable, to avoid multiple downloads.