Windows Installer keeps coming up because there is a program that is not completely or correctly installed on your computer. If you know the name of the program, uninstall it using Revo Uninstaller and install it again. If you don't know the name of the application, I suggest you run the Fix It utility provided by Microsoft. Alternatively, if you're using Windows XP or below, try to update Windows Installer. If you're using Windows Vista or above, update it through Windows Update.