2.  Disable any spy blocking software, Tweakmaster, download accelerators/enhancements etc.
Disable any antivirus application and anything unusual you have installed. Make sure you repeat this after every reboot before continuing.

3.  Try this:
WINUP: "Software Update Incomplete, This Windows Update Software Did Not Update Successfully" Error Message When You Visit the Windows Update Web Site.

4.  For Windows 2000, Windows XP, or Windows Server 2003.
Manually install the latest controls:
Download the controls from:
http://v4.windowsupdate.microsoft.com/cab/x86/unicode/iuctl.cab
Save them to your desktop. Extract the .cab file following the steps below:
A. Go to the desktop and right click the iuctl.cab file.
B. Click "Open".
C. Select all the files listed.
D. Right click on them and click "Extract."
E. Point to a known location (like the desktop) and click "OK."
F. Go to the location you selected and right click the iuctl.inf file.
G. Click "Install."

******************************************************************

For Windows 98 and Windows Millenium Edition.
Manually install the latest controls:
Download the controls from:
http://v4.windowsupdate.microsoft.com/cab/x86/ansi/iuctl.cab
Save them to your desktop. Extract the .cab file following the steps below:
A. Go to the desktop and right click the iuctl.cab file.
B. Click "Extract to."
C. Point to a known location (like the desktop) and click "OK."
D. Go to the location you selected and right click on the iuctl.inf file.
E. Click "Install."

5.  Otherwise try these:
Go to:
**Windows XP**
C:\windows\system32\drivers\etc\

**Windows 98/me**
C:\Windows

Right click on "hosts"
Click "Open"
Select Notepad for the application to open it.
Delete these lines if they are present:
akamai.net
Windows Update
Verify the following sites are fully trusted:
A. Open Internet Explorer.
B. Click "Tools," and then click "Internet Options."
C. Click "Security."
D. Click the Trusted Sites icon.
E. Click "Sites."
F. Clear the check box "Require server verification (https:)for all
sites in
this zone."
G. Add all five sites listed below.
http://windowsupdate.microsoft.com
https://windowsupdate.microsoft.com
http://download.windowsupdate.com
http://ntservicepack.microsoft.com
http://download.microsoft.com
http://V4.Windowsupdate.microsoft.com
https://v4.Windowsupdate.microsoft.com

6.  Try the Windows Update Checklist