Add Windows Login in Demo NAV 2009 - Windows7 OS

Dear all,

I have installed Demo NAV 2009 in my computer that is using Windows 7 operating system.
When I opened Microsoft Dynamics NAV 2009 Classic with Microsoft SQL Server, then I opened windows login to add other user, there is an error when I try to lookup windows account in my computer :

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Microsoft Dynamics NAV Classic

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The system failed to retrieve the global catalog from Active Directory.
This can be caused by network problems, or it can be caused by a lack of Active Directory functionality on your machine or the network.

Active Directory functionality is not available.
Contact your system administrator or your vendor for support.

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OK

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Then if I try to enter the windows account directly without lookup, I got another error :

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Microsoft Dynamics NAV Classic

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You do not have the required SQL Server permissions to perform the current security activity.

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OK

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What should I do to add windows login user in the computer that is using Windows 7 perating system? Because I do the same thing in the computer that is using Windows XP and there is no error result.
Please advice. Thanks before.