If a drive become to inaccessible drive, user can not access the files in the drive via File Explorer. And when you access the drive, Windows will ask you to reformat the drive. Of course,  please DO NOT format the drive.

The most reasons for the inaccessible drive are the file system parameters data on the disk have been damaged. With our data recovery software, you could easily recover your lost data with the following steps:

a.) Please download our Windows Data Recovery Software to your PC.

b.) Install our Windows Data Recovery Software to your PC.

c.) Launch our Windows Data Recovery Software, and then please choose "Advanced Recovery Module" to recover your data.

d.) Select the inaccessible drive you like to recover from the device list page, and then click "Full Scan" button.

e.) After scanning complete, please choose a file system (top 3 are recommended), and then click "Show files" button.

f.) If Advanced Recovery Module still not work, please try to use "Deep Scan Recovery Module"  to recover your data.

Recovery Tips:

DO NOT WRITE ANYTHING ONTO THE DRIVE CONTAINING YOUR LOST DATA!

DO NOT SAVE ONTO THE SAME DRIVE DATA THAT YOU FOUND AND TRYING TO RECOVER!
While saving recovered file or folder onto the same drive where they are located, you can intrude in process of recovering by overwriting table records for this and other deleted entries. It's better to save data onto another logical, removable, network or floppy drive.