There are a few mass storage devices that provide file and folder protection through write protection. Unfortunately, sometimes the files and folders cannot be accessed. Furthermore, some drives lack a write-protection switch but can still be set to read-only. Below are some possible reasons for this.
You might have bad sectors on your drive.
Malware or viruses have infected your storage media.
Disks are set to read-only in the Registry or in Property.
The media can no longer be writeable if the read-only mode is accidentally activated.
The read-only mode is accidentally activated and the media becomes un-writable.