Question: I have many JPEG files (pictures) on my USB flash memory. I give it to my customers to look at those pictures and choose one (then I make their order based on that selection). 
I want they can look at the pictures but don't can to copy or drag-and-drop them. 
Is there such a way?

I use Windows 7.

Answer: 
Unfortunately, if the file can be read - its raw data (1's and 0's) can be copied my merely reading them and putting the same bits into another file.

Even if you figured out how to copy-protect a memory stick, there are other things which users can also do including screenshots, print-n-scan, drive cloning, advanced file unlockers.. the list is endless.

Unfortunately, because of this - it is impossible to stop someone from copying the images.

You could always embed the images intoa piece of flash or similar - making copying the files directly harder to do. Couple that with a watermark and they have something not worth copying and requiring a it more effort - which will stop the basic copyist, but you can never stop everyone.
maybe outdated, but for whoever found this thread:

just make a brochure PDF that is password protected.
they still can copy it but can't deny the link between the image and your business.

and you can make them agree on non-disclosure-agreement in a contract. so your intellectual property will be kept secure.

that way when your PDF is copied and published elsewhere you'll get even more customers instead