title: "Unsupported 16-bit" error for a 32-bit app on a 64-bit Windows
body: <p>The app:</p>
  
  <ul>
  <li>Is a simple WinForms VB.net app built using VS2015 targeting x86</li>
  <li>No 3rd party controls. There are 7 references and all are <code>System.*</code></li>
  <li>Targeting .NET 3.5</li>
  <li>Code signed using a signing cert</li>
  </ul>
  
  <p>The environment:</p>
  
  <ul>
  <li>Runs successfully on Win7 Pro 64-bit, Win10 Pro 64-bit</li>
  <li>Runs successfully on Win7 Enterprise 64-bit</li>
  <li>But, Win8 Enterprise and Win10 Enterprise throw "Unsupported 16-bit Application" error (see link below)</li>
  <li>Each of the above mentioned systems are in different client environments (possibly different policies, different Anti-Virus etc).</li>
  <li>.NET 3.5 ought to have been installed on the machine. The main application that downloads WebUpdate.exe is also built to target .NET 3.5. If 3.5 is not installed, main application couldn't have been running and WebUpdate.exe couldn't have been downloaded/invoked.</li>
  </ul>
  
  <p><strong>Error Message:</strong> <a href="https://i.stack.imgur.com/sqbS0.png" rel="nofollow noreferrer">Unsupported 16-bit Application</a></p>
  
  <p>All the search on this error only bring up discussions about real 16-bit applications. But, this app built in VS2015 targeting x86 can't be a 16-bit application. Also, the fact it works on Win7 Enterprise/Pro and Win10 Pro. The only other topic points out that <a href="https://service.mcafee.com/webcenter/portal/cp/home/articleview;jsessionid=H0-fLEe0s83co8wKz4nt1VTsSrzUJYHUu1xtXy4fvIXptiBV90XU!-1547697373!-491800249?articleId=TS100483&amp;centerWidth=100%25&amp;lc=1033&amp;leftWidth=0%25&amp;pf=1&amp;rightWidth=0%25&amp;showFooter=false&amp;showHeader=false&amp;_adf.ctrl-state=2m6jjkstq_4&amp;_afrLoop=22896873790992#!%40%40%3F_afrLoop%3D22896873790992%26articleId%3DTS100483%26centerWidth%3D100%2525%26lc%3D1033%26leftWidth%3D0%2525%26pf%3D1%26rightWidth%3D0%2525%26showFooter%3Dfalse%26showHeader%3Dfalse%26_adf.ctrl-state%3D12i3uy5bpx_4" rel="nofollow noreferrer">McAfee might be changing the app to 16-bit</a> (?!).</p>
  
  <p>Any help/pointer/suggestion is appreciated.</p>
  
  <p><strong>Update</strong></p>
  
  <p>We installed the main application on a bare, brand new Windows 10 Enterprise; we couldn't repro issue. Upon running main application, we were prompted to install .NET 3.5. After installing, the main app ran fine. We had it check for updates; it downloaded WebUpdate.exe and run it fine. The whole update process completed successfully.</p>
  
  <p>This tells us that the 16-bit issue ought to be user machine specific. Yet, we've no clue what it could be.</p>