Windows Update site not seeing Win.XP

About two weeks ago, I made my weekly trip to the
Win.Update site to get any new updates,and was greeted with, Thanks for your interest. You must be using a Windos operating system to access this site. I am running Windows XP with SP1.
I never ran into this problem before. Has any one else had this problem ? If so, how did you rectify
it? Any help would be appreciated.
Thanks.