I have my Portable Hard Drive with 500GB..
and it has A LOT important files, I don't know why but one day I connected it to my computer
And it showed a little window that say " You need to format before using. "
I tried to connect it to other USB ports, but it didn't solve the issue.
The Portal HDD did not fall or something..
In Disk Management the format of the Portable HDD is RAW.