The WD my passport is not recognized by the computer .. It was wroking fine couple of weeks ago and am pretty sure it didn't fall or something.. its not recognized and not showing on my computer .. please I need help coz it contains all of my son's pictures from birth to his 2nd birthday.

Sadly you don't.
Dropping a hard drive and having it still work is something you should never expect.
You could pry the case open and put the drive it in an empty external drive case and see if it works, or try a new cable, but the most delicate part is the drive mechanism itself, and if anythings broken, that is most probably it.
You could probably get a replacement, maybe not WD, for around $60 and one I got on special $70 including postage from an online seller a few weeks ago had a 500GB WD drive in it.

Usually what has happened here is the usb interface has failed. The little hard drive with all your data is perfectly fine but the interface can no longer talk to the computer.

There are a couple of fixes. One is to send it in to WD who may or may not preserve your data. You can buy another passport and take the drive out and put it into the new drives enclosure. And third which is the way I've been fixing these is to go buy a usb drive enclosure. These start at $15 and up. Then you just take the drive out of your passport, plug it into the enclosure and you are back up and running.

This type of failure is common to all manufacturers.

The enclosure swap is something you can do yourself. The hardest bit is actually opening the case on the passport. Any computer shop should be able to do it for about $40 or less.

You've tried different USB cables; so, that cannot be the problem.

You've tried connecting to different computers; so, the problem is _not_ your computer.

What's left is "inside" the case:
* the USB-to-disk-drive adapter,
* the disk-drive.

Open the case, and remove the disk-drive, and connect it as a "slave" drive to some computer.
If it is detected, then the USB-to-disk-drive adapter that has failed.
If it not detected, then the disk-drive itself has failed.

FInd the serial-number on the Western Digital disk-drive, and enter it onto Western Digital's web-site, on the "check-warranty" page. If it's older than 3 years, the warranty probably has expired, unless you were "lucky" and got a 5-year warranty.

Western Digital has a "Customer Loyalty" program -- just buy a new Passport through their web-site, and cite the serial-number, and you'll get a significant discount on _their_ price (could be higher than your local retail computer-store) for a new (probably larger) Passport.

You might just need to assign a drive letter to it. Although this is generally automatic, something may have happened to cause it to lose it's format or drive letter. Check out the below link. I am pretty confident this will fix your problem.

http://www.online-tech-tips.com/computer-tips/how-to-change-the-drive-letter-in-windows-xp-for-an-external-usb-stick-or-hard-drive/

First thing to try is other usb devices as well as trying the drive in a different port. Preferably one away from the original to make it use a differeant hardware controller inside your computer. Also try unpluggin all usbs and rebooting a couple of times.

And try your drive in another computer to make sure it is working. if it isn't it may just be the enclosure electronics are the problem. If you have important stuff on it then you can try taking the drive out of that and putting it into a universal usb drive enclosure to get it up and running again.

you can't open it because this is a cause of viruses in your hardrive and your drive is infected i have this problem 2 weeks ago and fix it. open it from my computer right click go to manage and go to disk management open your drive from your WD. delete unrecognize files and hidden files.

Western Digital Passports work perfectly on USB ports 2.0 that supplies 5v of electricity with a max of 500mA. If your computer was manufactured more than 5 years ago, it may be using the USB 1.1 which is slower than the current.

In the end, I assigned a different drive letter to the device and it worked.

There's a lot of info out there on how to assign a letter. Here's one link:

http://lifehacker.com/software/windows/change-windows-drive-letters-167525.php

I have the 80GB WD passport and it suddenly stopped working one day.  The unit lights up but nothing else.  Finally I cracked the case open and found, as I suspected, that the drive is simply a SATA laptop drive with a SATA-to-USB conversion card built in.  I suspected that the card was **** so I disconnected it and used a USB hard drive adapter (http://www.tigerdirect.com/applications/category/category_slc.asp?CatId=3770&name=USB_Hard_Drive_Adapter) and I can read/write to the drive just fine.  Best part is that the adapter I use has its own power supply so I'm not pulling juice through the USB cable for a SATA drive. 
Even though mine "works" again I don't recommend these drives to anyone.  They're just not sturdy enough or well designed.

Does you drive make any sounds like these? If yes you have a mechanical problem and you should get a specialist to work on it.
If not - try to remove the drive from the enclosure and connect it directly to the computer to recover your files.