I posted something the same a couple of weeks ago:

After installing SP1 on for Windows XP, my computer would not allow me to login because it had a problem "checking the product key" of the computer. So I got into safe mode and did a system restore. Now, whenever I go to Windows Update, I get an error that says the following:

Can someone tell me how to fix this problem or reinstall Windows Update somehow?

you can uninstall all updates by going to Control Panel> Add/Remove Software .. only with SP1 you can only uninstall it if you chose to let the installer backup your files.. hope this helps...

I just want to uninstall the Windows Update tool used on the Windows Update site...

Anyone know how to do that?

Do you have the product key that is disabled by SP1?

No! Its an OEM version of XP Pro that came with my Dell...

Okay, did you read or do this:

Problem Description:

This may occur if Service Pack 1 has been removed from the machine either through System Restore or by reinstalling Windows XP into the same directory. We may see a page that states that the web page has an unexpected error or cannot display the Page that was requested

Resolutions:

Please reinstall Service Pack 1 or if you do not wish to reinstall the service Pack then we need to change the value for the CSDVersion in

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Windows

to 0.

1. Click on the Start button

2. Click on run

3. In the Open box type regedit and click Ok

4. Browse in the left frame to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Windows

5. In the right frame you will see the key CSDVersion please double click on this key

6. Change the value to 0 and click Ok

7. Please reboot the machine

--------------------------------------------------------------------------------

Issue Applies To:

Windows XP Client

No, I never read it...Where'd you find it?

Anyway, it finally works, and I guess it was that, that was causing the problem!

Thank dlt!

Glad it worked

http://v4.windowsupdate.microsoft.com/troubleshoot/

I scrolled down to: Unexpected Error or Cannot Display Page (Windows XP)