As you can see from the tray icon, the OM3 software has established connection with OM3.
Prolific device in device manager.
Driver detail shows that it's the same driver.
If you have problems with Vista and OM3, please write to email@example.com providing information from device manager.
Update: Only 32-bit versions are currently supported.
Update: If OM3 listed in the Device manager as "Prolific USB-to-Serial Comm Port" instead of "Prolific2 USB-to-Serial Bridge" that means you have searched the Web and installed an incorrect (previous) driver version before installing OM3 software, which comes with the correct driver. In this case please install the correct driver manually.