This is currently happening to 2 Win7 PCs where I work. Whenever the computer is locked the device plugged in and device unplugged noises play continuously. The users logged in when the noise happens are not local administrators, and it appears not to happen when a local admin is logged in or the PC is in safe mode. There are many other machines with the same hardware and same software image on the same domain that aren't having this issue. Any ideas would be great!