{ ... }
var
 strOLE: string;
begin
 strOLE = "YourCOMServer.Application" {your ProgID}
 if (CLSIDFromProgID(PWideChar(WideString(strOLE), ClassID) = S_OK) then
  begin
  { ... }
  end;
end;

{ ... }
const
 cKEY = '\SOFTWARE\Classes\CLSID\%s\InprocServer32'
 var
 sKey: string;
 sComServer: string;
 exists: boolean;
 Reg: TRegistry;
begin
 Reg := TRegistry.Create;
 try
  Reg.RootKey := HKEY_LOCAL_MACHINE;
  sKey := format(cKEY, [GuidToString(ClassID)]);
  if Reg.OpenKey(sKey, False) then
  begin
  sComServer := Reg.ReadString('');
  if FileExists(sComServer) then
  begin
  { ... }
  end;
  end;
 finally
  Reg.free;
 end;
end;