I have a Windows 8.1 Pro system with C:\ only containing the OS and some software. I also have a drive F:\ where I keep all of my files. Today I did a reset of Windows to get back to a clean slate.

One of the folders on F:\ is my Dropbox folder, so I've been going through help articles to make sure to simply point Dropbox to F:\Dropbox and letting it index those files in place, instead of redownloading ~300 GB.

One user described a problem where, because the Owner of the files was left over from his previous Windows installation, Dropbox began making conflicted duplicates of everything. This led me to go check out who the Owner is on some of my files.

Permissions, Ownership, UAC and ACLs have never been my strongsuit. Frankly, I don't know if my account was the Owner of all my files in the old system, and, if not, why not. I don't understand much about what determines who owns a file when it is created, downloaded, copied, whatever. Now that I'm looking at the Owner of a few of these files, I'm noticing a trend that most of the ones I've looked at are owned by an entity with a long string name that means nothing to me. S-1-5-21-blahblahblah. The blahs stand in place of a long set of numbers.

My best guess is that this string somehow was used in place of any file my user was the Owner of in my previous installation. Should I be taking ownership of all of these? Is there any harm in simply taking ownership of the entire Dropbox folder and its contents before I set up syncing?

  • Anyone care to explain the down vote? – bubbleking Nov 13 '16 at 0:52

Your guess is spot on. User accounts have a "security identifier" ("SID") that looks like S followed by hyphens and numbers. File ownership settings tend to use those SIDs. Then, when Windows encounters the SID, Windows looks up what user account is associated with that SID, and displays the user account instead.

Different installations of Windows are likely to have unique identifiers, so you'll have a different SID. When Windows encounters the old SID and can't find an associated user account, Windows doesn't know what to do except to just show what it knows. So, you see the SID.

If you'll never boot into the old installation of Windows again, then the old SID doesn't do any good, and having a file owned by that old SID also doesn't do any good. You're welcome to ignore the old SIDs. I would feel free to take ownership of that stuff, especially if you're the only one who uses the computer. The only way I would expect that might cause problems is if you do that on one of the directories used by the current version of Microsoft Windows. (Some stuff might be better suited to be owned by a SYSTEM account or something like that.) But if you're mucking in a graveyard that isn't used by any current installation of Microsoft Windows, I'd say go for it.

  • Excellent! As a follow-up, would it be better to assign ownership to Administrators instead of my own account (which is an Administrator), or is there much of a difference? – bubbleking Nov 12 '16 at 23:54
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    well, the administrators group has a predictable SID, so yes, setting the admin group as owner would alleviate this issue, at least in a workgroup scenario. support.microsoft.com/en-us/kb/243330 – Frank Thomas Nov 13 '16 at 0:46
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    Thanks @Frank. bubbleking: I would think an Administrators group might be more flexible. Later on, if you needed to re-create the group, joining that group might have less side effects than changing a current SID to match. However, I've mostly mucked with such permissions on Pro (or Server) versions of Microsoft Windows. Home versions might not be quite as easy to do some of these things (due to certain approaches being unavailable). – TOOGAM Nov 13 '16 at 8:08
  • @TOOGAM Oops. This is Windows 8.1 Pro. I forgot to mention this because I've been using Pro versions at home and at work for too many years. I'll edit the post. Also, I'm investigating writing a PowerShell script to take ownership of only the files owned by the old SID. Failing that, I'll just assign to Administrators. – bubbleking Nov 13 '16 at 14:40

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