There are a few systems that, for some reason, object to the .png file format that we use in the V4 installation screen, and therefore cannot show the installer properly. If this is the case for you, please try this workaround:

1. Download the 7Zip application and install on your system.
2. Right-click on Rhino 4 installer file.
3. From the menu, select 7-Zip and Extract files….
4. Select file location to extract the contents to and make a note of it.
5. Browse to this folder and look for the Rhinoceros subfolder.
6. Look for Rhino4_Setup.msi. Double-click to run this file to install V4.

The same process for V5 is described here.