title: From a GUID to a full path
body: <p>I'm trying to get the location of an installation so that I can perform an upgrade, I am using a WiX installer but I cannot use WiX's own upgrade mechanics because it nukes the config files and does not do the checks that happen in the Custom Action's UI.</p>
  
  <p>I have a bootstrapper which calls the .msi and I can easily get and set parameters within that .msi.</p>
  
  <p>In this situation- how could I get from a known, but dynamic, GUID to the file location of its install within the bootstrapper before the .msi runs and nukes everything. </p>
  
  <p>N.B. I cannot assume that the config file will remain the same between installs, or that I can grab the file faster than the uninstall can kill it. </p>