title: Wix Burn, how do I allow downgrading?
body: <p>So I've got a pretty simple burn installer, primarily to include .net upgrades or occasionally a driver pack for hardware our app needs to talk to.</p>
  
  <p>The MSI's we create support upgrading or downgrading.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"       
       xmlns:bal="http://schemas.microsoft.com/wix/BalExtension"&gt;
      &lt;Bundle Name="My App Name" Manufacturer="Company Name" Version="!(bind.packageVersion.MyAPP_MSI)"
              IconSourceFile="MyIcon.ico"  DisableModify="yes" DisableRemove="yes"
              UpgradeCode="{15E598EF-89CE-470B-8CEF-E32C8983DA33}" &gt;
          &lt;BootstrapperApplicationRef Id="WixStandardBootstrapperApplication.RtfLicense" &gt;
              &lt;bal:WixStandardBootstrapperApplication
                  LogoFile="$(var.CoreComponents.TargetDir)InstallerGraphics\Bootstrapper_Logo.png"
                  LicenseFile="$(var.CoreComponents.TargetDir)AppRoot\App License.rtf" 
                  SuppressOptionsUI="yes" /&gt;
          &lt;/BootstrapperApplicationRef&gt;
  
          &lt;Chain&gt;
              &lt;PackageGroupRef Id="NetFx451Web"/&gt;
  
              &lt;MsiPackage DisplayName="My full Application Name"  Id="MyAPP_MSI" SourceFile="$(var.Installer_MyAppMSI_TargetPath)"
                          DisplayInternalUI="yes" ForcePerMachine="yes" Visible="yes" /&gt;
  
          &lt;MsiPackage DisplayName="My Hardware Driver" Id="Installer_MSI_Driver" SourceFile="$(var.Installer_Driver.TargetPath)"
                      DisplayInternalUI="yes" ForcePerMachine="yes" Visible="yes" /&gt;
  
          &lt;/Chain&gt;
      &lt;/Bundle&gt;
  &lt;/Wix&gt;
  </code></pre>
  
  <p>We typically have beta releases and when a user wants to downgrade from a beta back to our stable releases they can't simply execute the old EXE installer.  They have to remove previous package from Add/Remove Programs explicitly to installer the older Burn EXE.</p>
  
  <p>This wasn't an issue with the MSI based install.  How do we get back to that functionality?</p>
  
  <p>Log</p>
  
  <pre><code>[0CB8:067C][2014-06-23T11:10:04]i001: Burn v3.8.1128.0, Windows v6.1(Build 7601: Service Pack 1), path:\\iop-filesvr\IOP\Builds\Main\8.1.240\IO Practiceware Client Setup.exe, cmdline: '-burn.unelevated BurnPipe.{197B8193-6EFC-4ED0-AF90-DE7205F13E65} {CD23A8AB-520B-4F5D-BCB9-98998C5A1EC0} 2216'
  
  [0CB8:067C][2014-06-23T11:10:04]i000: Setting string variable 'WixBundleLog' to value 'C:\Users\jeff\AppData\Local\Temp\IO_Practiceware_Client_8.1.240.0_20140623111004.log'
  
  [0CB8:067C][2014-06-23T11:10:04]i000: Setting string variable'WixBundleOriginalSource' to value '\\iop-filesvr\IOP\Builds\Main\8.1.240\IO Practiceware ClientSetup.exe' 
  
  [0CB8:067C][2014-06-23T11:10:04]i000: Setting string variable 'WixBundleName' to value 'IO Practiceware Client 8.1.240.0'
  
  [0CB8:067C][2014-06-23T11:10:05]i100: Detect begin, 2 packages
  
  [0CB8:067C][2014-06-23T11:10:05]i000: Setting string variable 'PrerequisitesVersion' to value '1.0.0.0'
  
  [0CB8:067C][2014-06-23T11:10:05]i102: Detected related bundle: {8d398d25-606f-419a-9b29-e3434aeb2485}, type: Upgrade, scope: PerUser, version: 8.1.241.0, operation: Downgrade
  
  [0CB8:067C][2014-06-23T11:10:05]i103: Detected related package: {7EA877FF-CE7A-49CE-8F76-D5A11EA7DD7A}, scope: PerMachine, version: 1.0.0.0, language: 0 operation: MajorUpgrade 
  
  [0CB8:067C][2014-06-23T11:10:05]i103: Detected related package: {8E8A7689-FB1C-4FE5-AF7C-95D499A342DE}, scope: PerUser, version: 8.1.241.0, language: 0 operation: MajorUpgrade 
  
  [0CB8:067C][2014-06-23T11:10:05]i101: Detected package: PrerequisitesMsi, state: Absent, cached: None
  
  [0CB8:067C][2014-06-23T11:10:05]i101: Detected package: ClientMsi, state: Absent, cached: None 
  
  [0CB8:067C][2014-06-23T11:10:05]i199:Detect complete, result: 0x0 
  
  [0CB8:076C][2014-06-23T11:10:16]i000: Setting numeric variable 'EulaAcceptCheckbox' to value 0
  
  [0CB8:076C][2014-06-23T11:10:16]e000: Error 0x80070666: Cannot install a product when a newer version is installed.
  </code></pre>