Windows Vista and Windows 7 users may find that the disc "spins down" and then Windows is unable to know that there is a disc in your DVD drive when you try to continue on with the installer.
To solve this, please insert the Rail Simulator DVD in to your DVD drive, and when the installer appears please cancel it. Now go to Windows Explorer (double click on My Computer on your desktop, or press Windows+E on your keyboard) and look for the drive that contains the Rail Simulator disc. You should copy the contents of the Rail Simulator DVD to a folder on your desktop, and once you have done that please keep the disc in the drive but run the setup.exe file from the folder that you have copied to your desktop. This should allow you to install the product correctly.
Once Rail Simulator is installed you can delete that folder that you placed on the desktop to clear up the space that is being used by those files, as they aren't needed for the use of the Rail Simulator product once it is installed.