I have a 600GB maxtor external hard drive. I bought it around two years ago and since filled the thing to capacity.
Just today, I was transporting the hdd in my car to a new location. Upon plugging in the external hdd the 'on' light didn't come on. Instead, it started making loud clicking noises every second or so (eeek!). I didn't know what to do so I turned it off immediately. I've tried turning it back on and it makes a fair bit of common seek noise (not clicking) before just powering itself down after a few seconds.
There are some files that I would obviously like to retrieve. My question is whether or not there is anything I can do? Presumably all my data is still there, but some physical mechanism has been damaged. Is there any hope of me repairing it? There are some files on there that I would not like anyone else to see either (bank account information, porn etc.)
Sounds like you may have heard the "click of death" caused by faulty head actuator movement. You can try to get it to work, but if you actually heard repeated loud clicks from the drive it may not be possible to recover your data without a very expensive clean room. You can try recovery programs like Recuva, but they only work if the drive is mechanically intact, which would not be the case if the loud clicking was what I suspect.
The loud clicking noise is not good, as noted by Realbeast, but if it is powering itself off you could have a problem with the external drive casing electronics. You can try taking the case apart and putting the drive in another case, or use an IDE\SATA to USB adapter, then see if it works normally. If this is a desktop hard drive, and you have a desktop PC, connect the drive temporarily inside of it as a second drive (If it is an IDE drive you may have to set a jumper on it to work). If the drive is bad, but stays powered on, then try a data recovery program. I have not tried Recova, but GetDataBack works great. It will sometimes access a drive even if your computer operating system cannot see it! Of course, try the simple things first. If my suggestion works, and you can access the drive in the operating system, see if you can just copy and paste it to your good PC drive. Hope this helps!