External drive just stopped being recognised by Windows

Install ReclaiMe file recovery from www.reclaime.com in your computer connect the hard drive and you will see the disc the way it was before. With a few clicks you will recover your files.

Leave it connected to your computer and try a restart.
If the folder is still showing as empty, power down the computer then disconnect the external drive.
Power on the computer and connect the external hard drive to a different usb port.
I had this exact problem with a 1000 Gb external drive that was full of movies and music. I thought it had all been lost .. After 2-3 days and repeated attempts of restarts and power-downs/different usb ports it suddenly was recognised again and has worked perfectly since

I had succeed to recover files from crashed hard drive with Asoftech Data Recovery program. It can recover data after deeply scanning your hard drive to look for lost data due to drives crash, physical damage,system sabotage, etc.You can download it and scan your hard drive for free to preview whether your files can be recovered
http://www.asoftech.com/articles/free-data-recovery-download.html

Were those files and folders something like System Volume Information, System Restore, Recycle Bin, and Desktop.ini? If yes then these are the folders that store the data about what is in the NTFS partition - deleting them makes the partition unreadable.
To recover your files from it you must install this program in a Windows pc
http://www.softpedia.com/get/System/Back-Up-and-Recovery/EASEUS-Data-Recovery-Wizard-Free-Edition.shtml
and run it. A better but paid program
http://www.easeus.com/datarecoverywizard/recover-formatted-partition.htm

Your WD HDD have been attacted by viruses for your computer or outside computer where you used it last. Make sure that you have an up to date antivirus software, scan your computer or the external hard drive, explore your computer, go to tools - folder options under view files & folders select show hidden files and folders apply and ok it.

try usin it on another computer,please scan for viruses

Did you install the drivers for the drive? Is it recognised in Windows as a device? If not, try reconnecting and Windows should prompt you to install the drivers, Assuming the drive is recognised by WIndows, then are a few causes for not transferring data. I've attached a link to Western Digital's FAQ regarding Data Transfer problems with your drive....

http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std_alp.php?p_sid=nCt181pj&p_accessibility=0&p_redirect=&p_lva=1017&p_li=&p_page=1&p_new_search=1&p_search_type=answers.search_nl&p_sort_by=&p_search_text=transferring+data

Several page of possible solutions are listed above.... however, you can refine the search if it is only happening when running specific apps or @ specific times. The answer you seek is located in this link. If you can provide more details on the type of file(s) you are trying to transfer and how, I'll refine the solution for you....

Make sure when you format archos its in file system fat32. I can only assume you need check folder permissions, which is why you cannot write to drive.

It is a problem with windows xp. *.avi files in windows may cause the problem.
Solution:
http://www.moviecodec.com/topics/3588p1.html