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How do I set permissions/ownership on my external USB hard drive in Windows 7 in such a way that I have write access to it at any Windows 7 machine?

Current situation is quite strange to me - the directories are owned by HOSTNAME\Administrators, I am user TOMAS, I am within this group (I am an administrator), but I cannot write to the disk. Can you please explain why?

And how to set it in such a way that I can operate from any Windows 7 machine. If I change ownership to Tomas, I will likely have an issue on different computer, where I use different user....

Maybe the best way would be to give full access to HOSTNAME\Users or to Everyone?

Output of calcs for the drive:

C:\Users\Tomas>cacls e:
E:\ Everyone:R

The Security/Owner dialogues:

enter image description here

enter image description here

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up vote 2 down vote accepted

The behaviour you see is probably due to User Account Control (UAC). Your user do not have Administrator access unless you press allow in the UAC prompt when you're doing operations that requires Administrator previleges. This includes reading/modifying files that can only be read/modified by the Administrator group. In this case, yes, granting full access to users will solve your problem.

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thanks @bill, but I don't understand well the UAC thing... I have 2 questions: 1) you say that I don't have administrator access, even if I clearly am an administrator? 2) How can I enable it? How do I run the UAC prompt? – Tomas Dec 1 '12 at 20:32
and no UAC prompt pops out when I try to write to disk... I think this is unrelated to UAC... – Tomas Dec 1 '12 at 20:36
So to prevent malicious software from modifying system files/configuration, even users in the Administrator group runs programs with a access of a normal user under UAC. The program can then indicate to the system that it wants to do some operation with the full admin previlege (commonly identified with the little shield icon) and the system will show you the UAC prompt. – Dec 1 '12 at 20:36
Then could you make a screen cap of the advanced dialogue in the security tab of the properties of that drive? Alternatively run cacls drive: and post the result (in the question or in or something). – Dec 1 '12 at 20:38
I've posted the information you wanted, please see my updated post. If you need to translate the dialogues from Czech, please ask me. – Tomas Dec 1 '12 at 21:57

Normally, unless you are using Active Directory, you give full access to Everyone.

The best clue to if you are using Active Directory is if your computer is joined to a domain.

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please explain this a bit to me... I am a Windows 7 beginner. I have just default Windows 7 Home Edition installation and I am a basic user, and I don't know what Active Directory is... and if I am using it or not. – Tomas Dec 2 '12 at 0:46
If you aren't sure, then it is very unlikely that you are using Active Directory. I added a dead giveaway if you are using AD. – surfasb Dec 2 '12 at 1:01
So, if I follow your logic, I am not using AD, so I give full access to everyone. But this is a direct contradiction of my problem, that I couldn't write on the HDD. – Tomas Dec 2 '12 at 1:25

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