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I'm running Windows 7 and have restricted access to a few of my folders through the Security Tab on the Folder Properties form. I've given full control to my account, administrators, and SYSTEM. But removed access for USERS.

This is working fine. But I'm wondering what will happen if my computer crashes/melts/is completely unrepairable but the hard drive is undamaged? Will I be able to access the files in these folders when the hard drive is plugged into another computer?

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An account is identified by random Security Identifiers (SID) generated for the computer and account name, thus the other computer will have no access. But don't worry, as those permissions don't apply you can add permissions yourself through the GUI or using CLI:

cacls X: /G Account:F /T
takeown /F X: /U Account /R

Where Account is an administrative account on the other computer and X: the path.

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What if you plug the hard drive into another computer with an identical computer name while logged in as a user with an identical account ID? – aireq Jul 15 '10 at 6:07
@aireq: Doesn't help. A security id is just a number, with no relation to the name. – harrymc Jul 15 '10 at 10:37
I have corrected my answer to make it less confusing, in a lower level a SID (long string) is generated which will be used to compare two accounts with each other, this string is guaranteed to be unique and it is very unlikely to find another account with the same SID. Just to show you an example, mine is S-1-5-21-661269417-1357230852-3651211512-1001. For information to a great detail see You can discover your own SID with if you want to... – Tom Wijsman Jul 15 '10 at 10:40
Ah ok so Windows tags the files/folders on the drives with the SID's of the accounts and what what access they should have? Yet on another computer users that are administrators can take ownership of files or changed security settings regardless of what the files are tagged with? – aireq Jul 16 '10 at 9:00
Yes, the administrator can always take over the permissions, even when you remove all permissions on the computer itself. The SIDs are stored in the Master File Table according to the Wikipedia page for NTFS: "$MFT describes all files on the volume, including file names, timestamps, stream names, and lists of cluster numbers where data streams reside, indexes, security identifiers, and file attributes like "read only", "compressed", "encrypted", etc." – Tom Wijsman Jul 16 '10 at 10:36

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