Clusters (Lost and Cross-linked)

The easiest way to describe cross-linked clusters is: two or more clusters that the File Allocation Table (FAT) or the Master File Table (MFT) points to that belong to more than one file. The clusters or allocations units are all the same size across the disk. The File Allocation Table has the same number of entries as there are clusters on the disk. This is how the FAT keeps the information on where the clusters are physically located on the disk. The FAT also stores the filename, date, time, size, file attributes, where the beginning of the file is located, and whether the cluster is at the end of the file (EOF) or what the next cluster number is.
Lost clusters are usually caused by files that are not completely deleted or files that have cross-linked clusters that are completely deleted taking the cross-linked cluster with it. This causes the remaining file that the cluster was cross-linked with to be missing that data. Also, corrupted data in the File Allocation Table itself can cause clusters to become lost. If this occurs you have a major problem. There are no provisions in the FAT system to help you recover data errors.
The recommended cure for clusters that are cross-linked, however, is to delete the files that both require the same cluster. Removing one file will not cure the problem as mentioned above.