procedure TForm1.Button3Click(Sender: TObject);
var
  f: TextFile;
  s,d: String;
  i: Integer;
begin
  d:=Edit1.Text;
  AssignFile(f,'name.txt');
  Reset(f);
  while not eof(f) do
  begin
    ReadLn(f,s);
    i:=pos(':',s);
    if d=copy(s,1,i-1) then
    begin
      Edit2.Text:=copy(s,i+1,Length(s)-i+1);
      Break;
    end;
  end;
  CloseFile(f);
end;