I recently cloned my main hard drive and re-installed Windows on it. I then put the cloned drive into an external enclosure to retrieve my backed-up files and was greeted by a scary message: “You need to format the disk before you can use it.” I put the drive back into my computer to see if it would boot into Windows and got another unpleasant message: “A disk read error occurred Press Ctrl + Alt + Del to restart.”
Going back into Windows using my healthy drive, I accessed the “sick” drive using Disk Manager. It turned out my cloned drive had somehow changed its file system from NTFS to RAW. I googled a bit and there were lots of solutions based on downloading a program to recover (maybe) the files and giving up on using the drive as a bootable disk. Finally I found a dead simple solution that put my disk back into 100% working order.
If you ever get these messages, don’t panic! Simply run a command prompt (Start -> Run -> type “cmd”) and then type “chkdsk x: /f” where “x” is the drive letter of the sick disk. In my case, it took a few minutes and at the end a bunch of errors were fixed. Afterwards the disk was working exactly as it should once more!