Before telling this Trick, I tell a story. One day My best friend come on my room. and he want my some important software and data. He just insert his pendrive and copy data into his pendrive. I am not interested to give my personal software and data to my friend. But I am not able to say 'NO' to my friend. So I use this simple trick to prevent inserting my friend's pendrive into my PC.
If you want to disable the pen drive on your computer than follows these steps:
