The PC-1100S is a model name associated with a Toshiba product, likely a specific laptop or device. In the context of a Windows driver, it refers to the software necessary for the device (such as a mobile broadband module, integrated hardware component, or a specific Toshiba peripheral) to communicate properly with your computer running Windows.

Unfortunately, without more context (e.g., whether the PC-1100S is a laptop, wireless module, or another device), it is difficult to pinpoint exactly which driver you are referring to. The term PC-1100S might correspond to a hardware component within a Toshiba laptop (for example, a wireless network adapter or a specific docking station), and the driver for that device is necessary for the hardware to function correctly on a Windows-based computer.