Most Windows administrators know that NTFS exists in a few different versions, one for each major iteration of Windows NT: 3.51, 4, and 5 (i.e., Windows 2000) and XP. Each revision of NTFS is backward compatible — in other words, a newer version of Windows can always read older versions of NTFS, although it does not create new volumes in anything except "its" version of NTFS. Some of these differences are obvious: for instance, NTFS in NT 3.51 had a placeholder in its structures for quotas, even though they weren't implemented yet, while in 2000, they are fully implemented. Some are not so obvious, and can lead to real problems on systems where more than one version of Windows Server is accessing an NTFS volume.
If you have a machine with both Windows 2000 and NT 4.0 on it, try this experiment. Use NT 4.0 to set an ACL on a folder or file. Boot into Windows 2000 and change the ACL for that object, then boot back into NT 4.0 and see what happens when you try to change ACLs once more. Odds are you'll get an error that reads:
The security information for path is not standard and cannot be displayed. Windows NT 3.x and Windows NT 4.0 support certain features such as DenyAccess Control Entries but cannot edit security information which uses these features. The information may have been modified by a computer running Windows NT 5.0, which supports these features and can edit information which uses them. Do you want to overwrite the current security information?
Saying "yes" to this will destroy all NTFS permissions on the object, but saying "no" will allow you to change permissions on that object in only Win2K. If something like this happens with a system object, or something for which you have no backups of the ACL information for, you may be in enormous trouble.
The best way to work around this is to download the Service Pack 4 Security Configuration Manager for NT 4.0. This utility allows NT 4.0's ACL editor to behave in the same manner as Windows 2000's ACL editor. It does not upgrade NTFS4 to NTFS5, however; the smartest way to do that is to move entirely to Windows 2000. If you can't do that, then this is the next best thing.
The SP4 SCM can be downloaded through anonymous FTP from ftp://ftp.microsoft.com/bussys/winnt/winnt-public/tools/scm/.
Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.