Seagate has admitted failures in a range of its disk drives, which prevent accessibility to user data.
As well as losing access to data on their disks, users find the disks are also undetectable to the computers they are mounted in.
The drives affected are the Barracuda 7200.11, the DiamondMax 22 and the Barracuda ES.2 Sata models.
Seagate said "the data becomes inaccessible to users but the data is not deleted" on the affected disks.
Seagate said the problem was caused by faulty firmware on the drives, which were manufactured in December 2008.