This article was previously published under Q83140
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This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.
When two (or more) files are cross-linked on the same cluster, do thefollowing:
NOTE: If you are running MS-DOS 6.2 or later, run ScanDisk, instead ofusing the following procedure.
Verify the error is accurate.
Not all versions and dialects of MS-DOS access disks in the same manner. If you booted from a floppy, the problem may be that the MS-DOS on the floppy isn't understanding the disk layout properly.
If Windows and another multitasker is active, all disk updates may not be complete. Exit from all other programs and from Windows before running CHKDSK.
Make copies of the cross-linked files on another drive or subdirectory.
Delete all crosslinked files. This is what actually fixes the File Allocation Table (FAT).
NOTE: If you are using Undelete and the Delete Sentry method of protection, remove the memory-resident portion of Undelete by typing UNDELETE /UNLOAD at any MS-DOS command prompt before you delete any cross-linked files.
Run CHKDSK to verify all is now well.
Manage the copies of the cross-linked files. If two files are cross-linked on the same cluster, one of them is good and the other is damaged. This can usually be determined in some way.
Reinstall or restore backups of the files that were cross-linked.
What Are Cross-linked Files?
MS-DOS organizes the disk's data area into sections called clustersor allocation units. Each file has its own directory entry, whichincludes the file name, size, attribute information, date, time, andthe cluster where the start of the file is stored.
The file allocation table (FAT) includes an entry for each cluster.Each cluster's entry includes either a code specifying that it is thelast cluster in the file, or the number of the next cluster used bythe file. Clusters can also be marked unusable, which CHKDSK reportsas bad sectors.
Cross-linked files occur when two or more files are both marked as"owning" the same cluster. Usually, the last file updated is correct;the other is correct except for the cluster's worth that is part ofthe other file.
For example, suppose you have two files, each 512 bytes in size. Eachfile requires one cluster. If both files are marked as being locatedin cluster 5, then cluster 5 probably contains the file with the laterdate. You can confirm this by looking at it (if it's a data file) orrunning it (if it's a program).
How Are Cross-linked Files Fixed?
The only way to fix the FAT in this case is to delete BOTH files. Whenyou delete the file, each cluster assigned to that file is marked"free to be used." If only one file is deleted, the cluster on whichthe cross-link occurred is marked unused, but the file system stillshows that cluster as belonging to the "good" file. This causesanother error (for example, CHKDSK may report a file allocation error,size adjusted or file allocation error, or file truncated). You alsolose access to the file from the part that was stored in the beginningof the cross-linked cluster to the end of the file.
MS-DOS should be able to make a copy of both files (although one willprobably be corrupt). If you don't want to delete both files, copythem to a floppy disk or another subdirectory before deleting them.