You can also prevent viruses on your flahs drive by creating a folder named "autorun.inf"
How does this method work?
As you might already know, viruses often create a file called autorun.inf in your external drive so that it can copy itself upon being inserted into a Windows machine. Windows will automatically run the little script, whether it's an automated installation setup.. or a virus! Therefore, if there's already a folder with that name, a file with the same name cannot be created, effectively disabling the virus to autorun itself.