title: Unable to delete post_perf_fw.dll file when upgrading or performing a rollback
body: <p>When performing an upgrade or doing a rollback on our software, the following error is thrown:</p>
  
  <blockquote>
    <p>Unable to delete file "C:\Program Files......\System32\post_perf_fw.dll </p>
  </blockquote>
  
  <p>When attempting to manually delete the file it complains with this error:</p>
  
  <blockquote>
    <p>The action can't be completed because the file is open in SQL Server (MSSQLSERVER)</p>
  </blockquote>
  
  <p>Windows 2012 SQL 2014 are present.</p>
  
  <p>Note that this issue has occurred on Windows 8.1 Pro and Windows Server 2012. This also happened when Microsoft SQL Server 2012 SP1 and SP2 was installed, although as of 07 Sep 2016 the machine with sql server 2012 with sp2 sql server installed has not been able to replicate this issue - it is unclear why.</p>
  
  <p>Any ideas on why Microsoft will load this file, and how to overcome this problem?</p>