alastairward,

You might want to try the device manager in your computer to see if you can see the drive information, and see if it's mounted and transferring information. The buzzing definitely doesn't sound good, and often times buzz or click noises signifies the end of a drive. If you are able to get it to connect, you may want to use that opportunity (if you can) to back up any valuable information on the drive.

Hope that helps.

--HDTech