Please make sure that the installer has the right name after downloading (on Windows the name should be "jinstall.exe"). Some browsers may rename the file.

If you do not have Java 1.4 or better on your system, make sure you choose the large installer including the JRE/JVM. Otherwise the installer will probably not start up at all (because it lacks Java), even if the download went ok.

Please note that after installation, the installer does not start up the program automatically. Instead, you should start up the program yourself (on Windows: hit the Start button, and find MadLab in the Programs menu). This should work, but if it does not, try to open the folder where you installed MadLab and start the executable MadLab file from there (on Windows it would typically mean opening the c:\Program Files\Madlab folder and double-clicking madlab.exe).