title: How can a perUser installation program deal with a perMachine older version of the program?
body: <p>This is similar to the question asked here: <a href="https://stackoverflow.com/questions/678002/how-do-i-fix-the-upgrade-logic-of-a-wix-setup-after-changing-installscope-to-pe">How do I fix the upgrade logic of a wix setup after changing InstallScope to &quot;perMachine&quot;</a>  </p>
  
  <p>Only in our case, the old version is "perMachine" and the new version is "perUser".</p>
  
  <p>I understand why you would not want a perUser installation to mess with a program that might be shared among several users.  But we need to go down this path.</p>
  
  <p>Currently, we are detecting versions of the old program by digging around in the registry and refusing to install unless they uninstall the old version first.  It isn't real user friendly.</p>
  
  <p>Are there any better techniques?</p>