NT/authority closes browsers in xp ?

Hi, Pros. One of my associates gave me a weird problem to solve: he says his web browser [IE in Win_xp] closes after an ominous message that reads something like: Your browser will be closed now. Please save your work. This closure was authorized by NT/AUTHORITY. I'm not sure I've been able to quote it exactly, but it's pretty much like it. He says he's fine as long as he doesn't click a download link. As soon as he wants to download something, it happens. I've never heard anything like that before, and I've been happily using IE on WinXP for a pretty long time. Any ideas ? Of course, I've asked him to get in touch with Microsoft support with his registration documentation. Regards.

Thanks, unmei. 

I'll sure tell my friend to try to restore to a point before this occurred. But, as I was thinking, could it be due to purchase of OS from a dubious source ? That's what crossed my mind at first (because the error message is so peremptory, just like those famous Windows Talkbacks. After all, you know that Big Brother is always watching us !). The second thing that had occurred was: could it be because of bad sectors in the HD (corrupting part of the OS) because he had scanned his HD thoroughly after the incident and found out that he had those bad sectors. (I had to change my HD because of bad sectors too. And I know that bad sectors can give rise to weirdest of symptoms, although I never heard what my friend is experiencing. We all know about This program has performed an illegal operation and will close error message, but a shutdown initiated by 'NT/Authority' is a new one.) Thanks again. Regards.