XP can't update ! HELP !!

HELP, I am in trouble !!

I am using a Dell machine, which runs a legal copy of Windows XP.

For years the Windows updates came in automatically. I didn't have to
worry about anything.

Then, since June this year, I noticed that there wasn't any more of
those "balloons" telling me of the windows update.

So I surf to Microsoft's Update site, at
http://windowsupdate.microsoft.com/w....aspx?ln=en-us

Only to be redirected to the following page:
http://www.update.microsoft.com/wind...&thankspage=2&

Which tells me the following:

"Thank you for your interest in obtaining updates from our site.

This website is designed to work with Microsoft Windows operating
systems only.
To find updates for Microsoft products that are designed for Macintosh
operating systems, please visit http://www.microsoft.com/mac/. "


Now, the funny thing is, I am using a genuine legal copy of Windows
XP.

I searched for answers online which led to this page:

http://www.winhelponline.com/article...-our-site.html

I followed the instruction at the page and put the command
"javascript:navigator.userAgent" on my IE8.

I got this:

Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)

I followed the instructions of the Winhelponline page and backuped and
then deleted the two registry entries at


HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \
Internet Settings \ 5.0 \ User Agent

and

HKEY_CURRENT_USER \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \
Internet Settings \ 5.0 \ User Agent



After that, I reboot the machine.

Still, I got the same "Thank you for your interest in obtaining
updates from our site." message.

HELP !!

What should I do to enable my XP to obtain the update?

I have scanned my system, no virus found.

I have not installed any new software in the past 2 years.

I have not done any meddling on the registry prior this episode.

And yet, the Microsoft update center is saying that my computer is NOT
running Windows OS.

What should I do next??

Please help !!