In most cases this is caused by the index file becoming corrupted. If the PC cannot read the index file it doesn't know how to handle the drive so it sends that annoying message. Normally causing you to panic that all your data is not gone.
I have found that the following steps are the most effcient when tryign to fix this type of issue on a PC.
- Take a note of the drive letter fo the disc that will not read.
- Open the Command prompt. 'Click the start button and type cmd and enter'.
- When the command promt opens thype the following:-
- chkdsk /f g: (Changing the last letter to the drive number that you noted earlier)
- Type Y and hit Enter and restart computer to resume disk check if you get the message "Chkdsk cannot run because the volume is in use by another process. Would you like to schedule this volume to be checked the next time the system restarts?"
- It may takes a long to finish run this process depending upon on the number of files and folders, disk speed, system resources, capacity of the volume.
I have tried this a few times on external hard drives when they have failed and it has worked for me. When this has finished the PC can see the drive again and all your files should still be available.