The RV7 configTool requires Microsoft .NET Framework to run.
Many users will already have .NET as a component of their Windows OS, however if you do not it is a free upgrade.
Available here: http://www.microsoft.com/net
Press the "Install .NET Framework 4" button near the top right of the page.
Also be aware, instead of using configTool, all config files can be manually edited in notepad.