The yellow exclamation on wd external usb drive is identified as " WD SES driver ".
I fixed that problem by clicking on one of these links below to download wd ses driver.
https://www.techspot.com/drivers/driver/file/information/16696/
Once driver downloaded.
Go to Device Manager, right click on the device which have yellow exclamation. Click on "update driver". Click on "let me chose driver in my computer ". Then, brows and click on the downloaded wd ses driver.
It not working for the first time. don't give up. keep trying. Failed. Restart pc and give it a try again and again.
For my case, after many time of trying, windows 7 displays " windows has successfully installed the device driver ", and the yellow exclamation just disappear. It took me 5 hours.
ouf. with perseverence and the problem identified. we can fixe the yellow exclamation.
Hang Vo