I have not use my WD my passport (4TB) for a while, just now tried to copy files to it, I have created a new folder on the external drive and then copied my outlook pst files to this new created folder. It shown on the disc with the new folder and also the copied files in the window explorer. I then turned off the laptop, unplug the WD external drive and then connected it to my desktop and turn it on. When using the window file explorer, it did not shown the newly created folder and file. I tried to reconnect it to the laptop and strange thing is the folder and file I created before disconnecting the disk also disappeared. Anyone has this experience and help me through? Thank you.
Thanks for the information, its seems that window help to repair the disc. Its is normal now. Anyhow below are my answers to your question for future reference in case it happen again. Thank you.