I have a passport 500 gb external hard drive and the problem is that everytime i plug it into a usb port the software appears but cant be installed due to too many password attempts. the hard drive doesnt appear in my computer and i never set a password. the only other option is to format but i cant coz i have important files in the hard drive. any help pliz

In most computers that are encountered, devices that are plugged into the USB ports are "plug & play" capable. There are numerous scenarios that can turn this function off inadvertantly such as a virus, data corruption or driver changes. In order to fix the issue and make an external device, such as a Western Digital Passport Elite hard drive "plug & play" capable, a user will have to make a few system changes. Click "Start" and "Run," then type gpedit.msc Click on "Administrative Templates," from the tree then click on the "System" folder. Double click on "Turn off Autoplay." Select the "Disabled" option and ensure it applies to all drives. Hope this helps,

Try using a different USB port and change your cable.

Maybe it's a power issue. Try a shorter usb cord or try a different usb port. If you are using an usb hub, try to connect the hard disk straight to the pc.

I have looked myself and it does not appear that WD tell you what model number drive is installed in their External drive units. This is not a problem because the actual drive used is not the limiting factor.
Even USB 3.0 will be much slower than a directly connected drive.

If you really need to know, you could open the case and check up on the specs on the model you find inside.

You will possibly find, as in the case an external drive I have of another brand, that mounts a WD drive that it is a model that come out first about 2 years ago, and is now finding it's home in external cases.
Not that there is anything wrong with that. The very latest drives will be a bit faster use a bit less power, but be wasted in a USB enclosure.
That said, the two year old drive i mentioned has quite nice specs, and i would use it as a replacement drive in a laptop happily.

The clicking sound is caused by the spindle inside the hardrive, because it was not removed properly. Just connect you external hardrive to your computer, if it makes the clicking sound again dont remove it yet, just restart your computer properly. In that way all the devices connected to the computer will be refreshed and properly shut down. If it is not detected still, unplug the haardrive then try another USB port. Recommended ports are at the back of the CPU if your using a desktop. These USB ports have higher voltage output that can power up all external hardrives properly.

This is a external hard drive and no need for you to install any software to a computer in order for it to work , this is a plug and play device you just need to wait for the computer to recognize it after you plug it to a USB port and once its recognize its ready to use.

right click START ,choose properties,choose taskbar then customize ,and select power surge...and select ALWAYS HIDE

this way you get rid of the pop-up message and just don't worry about it :))
Or
Delete all the USB ports in the devices manager, 
then restart the computer to let XP install all the USB ports again. Then go to the first USB port and right click on it and go to properties. Then on the advance tab click on do not show warnings

1. As always when oddities occur, run an anti-virus program scan and spy-ware scan.
   
2. Make sure there is an available drive letter between D and H, if you have a multi-card reader, multiple CD drives, etc. then you may be pushing the drive too far down the alphabet to initialize.
3. See if the drive will mount in safe mode, if it can then something is killing the device...run "msconfig" and use it to remove any TSR programs and services which you don't absolutely need in the system until the device can be initialized.
4. If you have the option between a regular USB port and a USB 2.0 port, remember to setup the drive in the USB 2.0 port.

may need to plug it in to a better outlet if you that option, worked for me. for a 500 GB external hd. i couldnt figure out why it only worked on occasion and on certain pc's and it all had to do with it not recieving enough energy.

Try usjng a different USB cable and a different port. Are you certain you are using a USB 2.0 port or is this an older machine with USB 1.0? If so, a newer 2.0 device might not work.