Found this on Windows Update Troubleshooter...
Problem Description:
User receives a 0x80072F76 error when visiting the Windows
Update Site. The Windows Update.log file will have error
entries similar to the following:
2002-11-25 23:25:11 04:25:11 Error IUCTL Failed to
download iuident.cab from http://
windowsupdate.microsoft.com/v4/ to C:\Program
Files\WindowsUpdate\V4\temp (Error 0x80072F76)
Resolutions:
This is a blocking issue. The client computer is unable
to connect to a component of the Windows Update site.
Most likely this is due to misconfigured proxy/firewall
settings,
incorrect DNS entries or some application running on the
client computer that interacts with Web connections and is
blocking the connection. Here are a few ways to try to
resolve this issue:
Suggestion 1
===========
Check your HOSTS file (it may also be called HOSTS.SAM)
and make sure you don't have any static IP entries for the
Windows Update web site listed in the file. If you are
running Win98/ME, the HOSTS file will be in this folder:
C:\Windows
If you are running WinNT/2K/XP, it will be in this folder:
C:\WINDOWS\system32\drivers\etc
You can use Notepad to open the HOSTS file. You may need
to "tell" Windows to use Notepad to open the file.
Applications like web accelerators, TweakMasterDNS, etc.
can add static IP entries for the Windows Update site into
your HOSTS file and when this happens you will get the
0x80072F76 error message.
Suggestion 2
===========
Check your firewall/proxy settings and also try disabling
your firewall. This error is the result of your PC's
inability to connect to a component of the Windows Update
site. Disable all 3rd party applications (including anti-
virus) before accessing the site.
Suggestion 3
===========
You may be able to resolve this issue by adding the
following Web sites to the trusted sites list in Internet
Options:
http://Windowsupdate.microsoft.com
http://V4.Windowsupdate.microsoft.com
https://v4.Windowsupdate.microsoft.com (Note: The https
is correct)
http://Download.Windowsupdate.com
To add these web sites to the list, follow these steps:
1. Open Internet Explorer.
2. Click "Tools," and then click "Internet Options."
3. Click "Security."
4. Click the Trusted Sites icon.
5. Click "Sites."
6. Clear the check box "Require server verification
(https

for all sites in this zone."
7. Add all four sites listed above.
Suggestion 4
===========
This issue may be resolved by adding the Windows Update
sites to the exceptions list in the Internet Options Proxy
Settings.
To access the Exceptions settings:
1. Open Internet Explorer
2. Click "Tools" and then click "Internet Options."
3. Click "Connections" and then click "LAN Settings."
4. Click "Advanced" and add windowsupdate.microsoft.com;
v4.windowsupdate.microsoft.com, and
download.windowsupdate.com to the exceptions list.If you
run other proxy/firewall software, then add the sites to
the exception list for those applications as well.
-----------------------------------------------------------
---------------------
Suggestion 5
===========
As a test, try this link:
http://windowsupdate.microsoft.com/v4/iuident.cab
When you click this link, you should see a popup message
asking if you want to Open the file, or Save it to your
computer. If you are unable to connect to this link and
see a Page Cannot Be Displayed-type error, then this
confirms that some aspect of your Internet connection is
preventing you from reaching the Windows Update site.
Suggestion 6
===========
This error may also occur with Mailgate from
http://www.mailgate.com/ previous to version 3.5.171 beta
where the issue seems to have been corrected.
The excerpt below is from the release notes for the
MailGate 3.5.171 Beta:
1.1 SDR0137 - Added support for the HTTP HEAD command in
the Web proxy. This command is used by the Microsoft
Windows XP update service.
-----------------------------------------------------------
---------------------
>-----Original Message-----
>I can't access windows update to get a list of available
updates.
>
>My error number is: 0x80072F76
>
>Please Help!
>Thanks
>-Pete-
>.
>