I am trying to restore files that were created in another build of Windows 7 that had their permission changed so that only the owner of the file could read and access them. Because I am the person who created the original files and changed the permissions, why can’t I access them now when I am using the same login name and password as I used with the previous instance of the operating system?
Perhaps I am being much too hopeful thinking that permissions in a Windows environment would behave the same as in Unix. I had a Unix disk where I changed the permissions of the files in a folder to be readable and writeable only by me. When I created a new system, as long as the user name and password were the same, the files would be accessible. How can I get to these Windows 7 files now?
I hate to say it, but Windows is not Unix. Not even close. 
Windows security model is very different from Unix. Even in this situation, however, if you were on a Linux machine, you’re not necessarily guaranteed that the same username and password will map across different file systems that were created on different machines.
But that’s neither here nor there. The point is that Windows doesn’t work the way you think it does. Let’s look at what’s happening on your Windows machine.
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User names and the GUID
When you create an account under Windows, it creates what’s called a GUID, Globally Unique Identifier. Basically, it’s a big, random number that identifies your account on that machine.
The GUID never changes. It’s basically the low-level identifier of your account on that machine. That’s how you can rename an account and still access your files.
But when you create another account on a different machine using the exact same username and password as you did on that first machine, the GUID is going to be a completely different number. In other words, the username and password on one machine may be the same as the username and password on another machine, but the GUIDs won’t match.
And it’s the GUID that matters.
Networks just don’t care
What complicates this whole scenario is that your network access isn’t looking at mismatching GUIDs. If you use the same username and password on different machines, your network considers it enough of a match and allows you to access things across the network.
That’s fine. It’s actually kind of handy but when it comes to physically moving a disk from one machine to another, that doesn’t work. The user ID and password is not what ultimately identifies the ownership of the file on the disk.
Getting permission with two different GUIDs
I have an article on this called “How do I gain access to files that Windows says I don’t have permission to access?” This is a very common scenario when we’re actually taking disks from older machines and plugging them into newer ones with the intent of recovering the data.
What you need to be is the administrator on the machine that you have these disks installed on and that article will show you a couple of different permissions related commands that will essentially remove all of the restrictions on all of the files so that any account can access them and then you can do with them what you need.
Good luck!
