a message continually comes up on my screen telling me I should format the disk in Disk K - my 1t Astone hard drive. Many important docs and pics are saved on it. If I click 'format the disk' will I lose them all? Why does it need to be formatted?
The "Not formatted error" problem often happens for many reasons. Therefore, you have no need to worry. As cin19 says, you'd better backup all your important data on a different drive in case of data loss and format the drive to return its normal use.
But, if you cannot access the inner data for backing up, you can try a hard drive recovery freeware that can easily retrieve all your wanted data back. It is worth a shot since it has ever completely saved all data of my brother from a formatted flash drive. You can visit it here: http://www.freeware-fix.blogspot.com/2013/02/flash-disk... Important note: You should not forget to format this drive after the recovery process.
You should remember to back up all your important data all the time.