Автор: http://www.swissdelphicenter.ch

uses
   ImageHlp;

 function SearchForFile(const ARootPath: string;
                        const AFileName: string;
                        var APathFound: string): Boolean;
 var
   Found: array[0..500] of Char;
 begin
   FillChar(Found, SizeOf(Found), #0 );
   Result := (SearchTreeForFile(PChar(ARootPath), PChar(AFileName), Found) = True);
   APathFound := ExtractFilePath(Found);
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 var
   APathFound: string;
 begin
   if SearchForFile('C:\WINDOWS\', 'winhlp32.exe', APathFound) then
     ShowMessage('winhlp32.exe found in: ' + APathFound);
 end;