You can find out your current system version by select About This Mac from the Apple menu. To make sure it is updated, select Software Update from the Apple menu. A Mac from Nov. 2011 is probably running "Lion," and the latest version of Lion is Mac OS X 10.7.4.
But that should not affect the connection of an external hard drive. There are no special updates for connecting standard external drives.
Does the external Toshiba drive connect by USB port? Is it the smaller type that gets power from the port (no conection except for the one cable), or is it larger (with its own power supply)?