When you install Windows NT 3.51 and start Disk Administrator for the first time, Windows NT will write a disk signature to the drives before opening the Disk Administrator window. The first time Disk Administrator is opened, drives and partitions appear correctly, but if you close and reopen it, some of the partitions are lost and incorrect information is displayed on the others. This only happens if there are more than two logical drives in an extended partition when Disk Administrator attempts to write a fault tolerance signature. This problem will not occur if a signature is already present.
Faulty calculations result in the corruption of logical drives in an existing extended partition.
It is possible for a system to remain functional after the partition table is corrupted. The nature of the corruption is such that partition table data is written to incorrect locations on the disk which may lie in the middle of user or file system data. Provided this information is not overwritten, the partition table entries may still identify the layout of the drives sufficiently well that Windows NT can continue to access the drives. However, this is an unstable situation and access to the partitions will be lost when the table entries are eventually overwritten. If the table entries overwrite existing data, user data or file system integrity are compromised immediately.