0x800a0046 Windows Update Error

# The security descriptor does not let authenticated users run Windows Update.

# The Impersonate a client after authentication policy is missing the Administrator and Service account from the list of Users and Groups.

To resolve this error, use one of the following methods:

Resolution Suggestion One:

# Remove the user account that is experiencing difficulty from the Guests or Limited account groups:

1. Click Start, click Run, type control admintools, and then click OK.
2. Click Computer Management.
3. Expand Local Users and Groups.
4. Select Users.
5. Open the account that is used to access Windows Update.
6. Click the Member Of tab.
7. Select the user account that you want to remove, and then click Remove.

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Resolution Suggestion Two:

# Set the Security Descriptor:

First stop the Automatic Update Service:

1. Click Start
2. Choose Run
3. Type cmd and then click OK.
Type:

sc sdset wuauserv D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)
(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)
(A;;CCLCSWLOCRRC;;;AU)(A;;CCLCSWRPWPDTLOCRRC;;;PU)

and then press ENTER.

You will receive a "Success" message.
4. Type Exit to close the command prompt.
5. Try Windows Update again.

(NB - You should be able to confirm that this has worked by typing:  sc sdshow wuauserv  in a command prompt!)

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Resolution Suggestion Three:

# Verify the Local Administrator and Service account are added to the "Impersonate a client after authentication" security policy.

1. Click Start.
2. Point to Programs.
3. Point to Administrative Tools.
4. Choose Local Security Policy.
5. Expand Local Policies.
6. Choose User Rights Assignment.
7. Double-click to open the Impersonate a client after authentication policy.
8. On the Local Security Setting tab, add the Service and  Administrator to the list of Users and Groups.
9. Click OK.
10. Restart the system.

From a newsgroup posting:

Another possible cause for the 0x800a0046 error is that the "Automatic Updates" service is not running as the correct user. To check/fix this, find "Automatic Updates" in the services list and choose "properties". Then select the "Log On" tab and make sure the button for "Local System Account" is selected. If it isn't, then close the window and restart the system.

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