title: VB6 IDE Slowness and 'VBKeySave5' in the Registry
body: <p>What is the registry subtree <code>HKCR\VBKeySave5</code> for? Why does it have such a huge effect on VB6 IDE performance?</p>
  
  <p>Background:</p>
  
  <p>One of our development PCs (Windows 10 x64) had a very slowly loading VB6 IDE. The IDE was slow to load initially, and very slow to bring up the project references window. (Tens of seconds, or even ~minutes).</p>
  
  <p>Purusing the registry for one of the libraries used by the project revealed the subtree <code>HKCR\VBKeySave5</code>. Under this subtree were thousands of entries that looked like the usual COM marshland of GUIDs, class IDs, classnames, etc. which you get with VB6 DLLs, etc.</p>
  
  <p>Deleting this key and everything under it made the IDE perform immeasurably faster - basically it would load and then show the references window instantaneously.</p>
  
  <p>Nothing bad seemed to happen as a result of this.</p>