title: Visual Form Inheritance problem. "cannot inherit from (parent form). Contains a component that does not support inheritance"
body: <p>I have a base form with descendents. The base form has a TElRelDataSource on it (from ElPack v4.00). When I open the descendent form I get an error "cannot inherit from (parent form). Contains a component that does not support inheritance". This is with the ancestor forms open (there are two), to avoid the "ancestor for (parent form) not found" error.</p>
  
  <p>Delphi 7 doesn't (AFAIK) support finalising classes, but this seems to be a standard error message. It's in the index for "Tomes of Delphi: Troubleshooting" but I don't have a copy of that and I'm reluctant to spend $US60 to read an entry like "this is why you should avoid VFI" (being pessimistic about the contents of the book). Other than that, no references in Google or Bing.</p>
  
  <p>This is in code that I've recently inherited from someone who left a while ago and I'm the first person to change it since they left. Which means I can't ask how he created the offending form.</p>
  
  <p>So, how do I get around this error message?</p>