Is it possible to identify a USB device by a unique identifier like an Operating system has Mac-ID, Harddisk ID, Ethernet card ID has unique identifiers? I know one can easily change the volume serial number of USB partition or it could be changed when user Formats it.
But is there an ID some kind of 'USB Harddisk ID or USB Hardware ID' which could be retrieved via MFC's (Visual C++ or C#) using the WMI Service? Will such an identifier be unique to the physical device? Kindly clarify...
The closest equivalent of a "unique number" available in any USB device is the VID and PID, the vendor and product IDs. It is used to identify the device and install the proper driver for it. However, it is the same set of numbers for the same product, it is not good enough to identify the particular device you have in your hand. And thus useless to implement a license verification procedure, presumably what you are after.
Only certain kind of USB devices implement a serial number. You get it by accident from a flash drive due to the drive formatter generating a volume serial number. Useless as well, it can easily be changed. A USB wifi adapter could work, the manufacturer must generate a unique MAC address.
There's one class of USB devices that are perfect for this goal. The generic name is "dongle", they are made for this. When you buy one you also get software that you can link into your program that provides a tamper-proof way to verify the license number, another important part of a license verification procedure and usually the weak link. More about dongles in this Wikipedia article.