autorun.inf is used to autorun programs and set icons in Windows when you insert media. It was a great idea.. put in a CD and automatically you get some nice menu where you can choose to install a program, view its documentation, etc.
The problem, it was an AMAZING way for viruses and such to spread themselves. You plug in your USB stick to your desktop and if your desktop is infected it installs itself on your USB stick with an autorun.inf. You plug that USB stick into some other desktop.. and now that desktop will run the virus and get infected. Great little mess to clean up too.
My guess is that since this file keeps recreating itself, someone, somewhere that has access to that location is infected with such a virus and its trying to spread itself. So you might want to stop trying to delete that file and figure out who is infected.
This is all just speculation of course, but I know someone that had this exactly problem years ago and it turned out that the network was spreading some kind of bad egg around the network.
Good luck.