I’ve had the hardest time installing Calibre book reader and ebook converter on my Windows 7 64 bit machine with no idea why. It kept erroring out with the message “Calibre setup wizard ended prematurely.” I finally got it to set up by following these steps:

  1. Choose a directory other than the default like C:\Calibre
  2. Choose “Advanced” when setting up
  3. After you hit the Advanced button, uncheck all the options except the first one which installs the main program

After this I finally got it to install. If you still have problems I recommend trying different options on the first tab to get it to install.