A USB device enumeration process implemented in a USB device is described. The USB device first detects a type of the operating system (OS) of the USB host connected to the device, and performs device enumeration using a process selected from multiple stored processes based on the detected host OS type. To detect the host OS type, the USB device first presents itself to the host as a USB MSD or HID, performs device enumeration to collect OS behavior factors from the host, and determines the OS type from the OS behavior factors. Thereafter, the USB device performs actual device enumeration by presenting itself as the USB device it actually is, using an enumeration process specific to the detected host OS type. The multiple stored enumeration processes are customer configurable. Further, a method is provided to stop an enumeration process when the host is in a BIOS stage.