There is a number of viruses that create autorun.inf files on all writable drives, as soon as you stick any USB or memory stick in your computer it creates it. Some of the viruses display corrupt right-click menu’s, stop allowing direct access to c:\ through “My PC”, and cause other irrational behaviour.

The best solution I’ve found so far is to simply display all hidden files and folders in the USB Memory stick, delete the current autorun.inf, create a folder named autorun.inf, this way the virus can’t create or replace the file as it is really a folder. I haven’t been infected since, and it’s good protection if you are moving the memory stick around from pc to pc.

A friend of mine told me about this procedure, so I verified it on internet and I found a bit more information that might be helpful if you’ve got one of these viruses:

http://bleuken.i.ph/blogs/bleuken/2007/06/29/viruses-that-uses-autoruninf/