You are really in a state of shock when the Lacie hard drive not working. There are many important files that you have stored in it because the Mac hard drive was out of storage space. The lacie external drive is a great option for storing files as it can be transferred easily. However the data can get lost from the lacie drive in many cases like when the lacie drive is detached from the Mac system accidentally or when the system shut down abruptly. Sometimes the lacie hard drive not working because it is not getting enough power to work. The file system of the lacie drive can get corrupted because of improper partitioning or formatting. If the lacie drive is infected by virus then the corruption can occur. you can try to reconnect the drive and see if it works if not then you have to format the drive to remove any corruption. When the lacie hard drive not working problem is resolved you recover the data you have lost which can be done using any backup. If the backup is not available the use the Lacie drive recovery software to restore all your files. You should download the software and see its benefits.