If you have an old computer that has not been updated for last several years you need to check for the following.
The Medical Tests Analyzer is written for .NET Framework 4.0. Before launch Medical Tests Analyzer setup package you need to install on your computer the .NET Framework redistributable package dotNetFx40_Full_x86_x64.exe. It is available as a stand-alone executable file. As a result of downloading you will receive a file named dotNetFx40_Full_x86_x64.exe. Use dotNetFx40_Full_x86_x64.exe for deployment purposes.

Visit Microsoft Download center

Download dotNetFx40_Full_x86_x64.exe

Before download dotNetFx40_Full_x86_x64.exe please read .NET 4.0 Framework Redistributable End-User License Agreement
Note that administrator privileges are required to install dotNetFx40_Full_x86_x64.exe. If you have previously installed the .NET 4.0 Framework SDK or Microsoft Visual Studio 2010 (or later), you do not need to install dotNetFx40_Full_x86_x64.exe.

How to detect .NET 4.0 framework installed or not?
You need the MS .NET 4.0 framework to run this software. The .NET 4.0 framework is a foundation that a wide variety of software can build on without repeating basic information, and vertical apps can be very small in size. The .NET 4.0 should not hurt your PC in any way. Here is how to check if you have .Net, and what version:
Go to "Control Panel" of your PC. Then select "Programs and Features" ("Add or Remove Programs" for Windows XP) and see if it is listed there. If it is - you have it, if it is not - you need to install it.
If there is the following record presented in the Programs list:

Microsoft .NET Framework 4.0

you do not need to install .NET 4.0 Framework. Also if you have latest versions of .NET listed (4.5) you do not need to install. Otherwise you need to download and install .NET 4.0 Framework.