How to remove shortcut virus from usb-flash-drive

This tool and this tool both look like they would serve the purpose you are trying to achieve. The NirSoft interface is a little less direct, but I trust the author and his ability to write code. The second seems to have a more useful UI in your situation, but I have no history with the website or author.

ProcessExplorer is another easy way to do it, simply open up ProcessExplorer, hit Ctrl+F, and then type the name of the file. ProcessExplorer will list all the programs using that file. If the WhoLockMe tool doesn't work for you, I'd recommend ProcessExplorer next, simply because it has so many other useful features.