WESTERN DIGITAL EXTERNAL HARD DRIVE

THis The System Make a connecting noise? as it make when a usb devise is connected sucessfully?

if it does then:

1. leave the drive connected and restart the PC. and then disconnect and attach it again. and wait for a minute or so.
then see if it is been detected.

2. leave the drive connected and insert XP cd and boot the system. and when it shows partions to install XP can you see a Separete disk below showing [MBR] memory.

if it does then it means there is a problem with the windows and reinstall the windows, but 1st try reinstalling USB driver.

My hard drive was dead and wasn't recognized by the computer, it didn't even start, just a few clicking noises, which according to some of the experiences is the same as a DEAD Hardisk. Anyways, as I read that sometimes this happens as a result of a hit, well, I wacked my HD as a last hope for it to recover its "memory" (as in the movies) and believe me or not, it worked! I don't know if this might help yours, but it saved mine! 
The way I did it was like this: I started the pc and when the HD started to run and I heard a couple of clicks, I hit it against the table while in vertical position (assuming that the arm of the HD might slightly move better that way) one time, and then when the spinning and the first click was heard agin I hit again. After that I heard the typical searching sound of a HD, and you can imagine I started to pray that what I heard wasn't my anxiety sound (if it has any). Now I am a firm believer in the old trick of whacking the old TV to get the vital signal back! 
Good luck to you too!