The Promise Technology Inc. Ultra66 IDE Controller is a hardware controller card that allows your computer to connect to and manage multiple IDE (Integrated Drive Electronics) devices, such as hard drives or optical drives, through an IDE interface. The "Ultra66" part of the name refers to the data transfer speed supported by the controller, which can transfer data at a maximum speed of 66 MB/s (compared to the original IDE interface's 33 MB/s).
The Windows driver for the Ultra66 IDE Controller is necessary for the operating system to recognize and properly communicate with the controller card. It allows Windows to manage the IDE devices attached to the controller, enabling functions like data transfer, disk access, and proper drive management. Without the driver, Windows may not detect the Ultra66 controller, or the connected drives might not function correctly.