The USB Reader V3 Windows driver typically refers to a software driver for a USB card reader or USB device reader. These devices are commonly used for reading data from memory cards (such as SD cards, microSD cards, CF cards, etc.) through a USB port on a Windows computer. The "V3" version indicates a particular iteration or model of the USB reader. The exact type of reader will depend on the manufacturer and the specific device model (e.g., Kingston, SanDisk, Transcend, etc.).