title: Prevent multiple installs
body: <p>I’m building installer for my product, using WiX Toolset 3.10.2.</p>
  
  <p>Have two WIX projects in the solution, one builds MSI from compiled binaries, another builds setup.exe from the MSI using WixStandardBootstrapperApplication.</p>
  
  <p>If I increase version, it works OK, offers to upgrade.</p>
  
  <p>If I launch the same installer second time, it works OK, opens with “Modify setup” screen.</p>
  
  <p>The problem is, after I rebuild the installer without increasing version, it fails to detect previous install, and happily installs second time (so the “uninstall” control panel has multiple identical items).</p>
  
  <p>How to stop that, and only allow single installed instance of the product?</p>
  
  <p>The MSI:</p>
  
  <pre><code>&lt;?include "..\Version.wxi"?&gt;
  
  &lt;Product Id="*" Name="xxx" Language="1033" Version="$(var.vvvVersion)"
          Manufacturer="yyy" UpgradeCode="0d88cab0-d278-43bb-b891-607bc01c4dec" &gt;
      &lt;MajorUpgrade DowngradeErrorMessage="A newer version of xxx is already installed." /&gt;
  </code></pre>
  
  <p>The EXE:</p>
  
  <pre><code>&lt;?include "..\Version.wxi"?&gt;
  
  &lt;Bundle Name="xxx" Manufacturer="yyy" Version="$(var.vvvVersion)"
          UpgradeCode="eac46fb0-09d1-4c29-8fc1-984dddb35e50"
          IconSourceFile="$(var.SolutionDir)applicationIcon.ico" &gt;
  </code></pre>