Hard disks can fail. In an app I'm working on, I use Winmgmt Service to get the CPU serial number and OS serial number, but I must confess that I haven't tried it under various permissions.

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>Hello Hilmar,
>
>If you find a solution (either here or elsewhere) to this problem could you please let me know about it. I do the same thing with an app.
>
>Thanks.
>
>>We have been using a system based on the hard disk's serial number to stop the program from working on non-authorized computers; in Windows 7, this system fails miserably. It took me a while to figure this out, but it seems that this is on purpose: the Windows function that is supposed to return the hard disk's serial number fails, due to privacy concerns.
>>
>>Is there any way around this? For example, I might request administrative permissions for the program - although right now, I don't know how. Also, this verification would have to be done every time the program starts, and it would be quite a hassle for the user to authorize the program every time it starts.
>>
>>We have also considered getting the volume number instead - the information shown with the "vol" command in a DOS window. Once again, I am afraid this might fail if the user doesn't have administrative rights.
>>
>>The possibility of writing a random value to some obscure Registry key also occurred to me, but once again, I am not sure what sort of access rights this requires.
>>
>>Or how is this situation normally handled?
>>
>>TIA,
>>
>>Hilmar.