Windows sometimes does that, it basically reminds you to check windows update from time to time.
I don't know if you can do much about it, I've always allowed my 'puter to visit the page and the next time it was gone again, the registry change is probably to remind itself to wait a set amount of time before the next visit. You could just allow the registry change, and see if that gets rid of it. It is a Microsoft page so that should make the change 'legal'.
