USB_ModeSwitch is a small mode switching tool for controlling "flip flop" (multiple device) USB gear
Several new USB devices (especially high-speed WAN stuff, they're expensive
anyway) have their MS Windows drivers onboard; when plugged in for the first
time they act like a flash storage and start installing the driver from there.
After that (and on every consecutive plugging) this driver switches the mode
internally, the storage device vanishes (in most cases), and a new device (like
an USB modem) shows up. Some call that feature "ZeroCD".