You could try using
Unlocker 1.8.0. Simply install the program, and right click the file/folder in question. Then from the menu choose "Unlocker". The program will tell you if there are any programs locking the file, as well as give you options on how to handle it (such as delete it, rename, move), and if it's unable to delete the file it will ask you about doing so when you reboot.