Thanks guys. Das Boot (one of my fave movies by the way), why do you think my name is Chris?
Yes it is an automatic update activated in XP. Should I always click 'yes' to update? Where do these updates come from? I assume the one yesterday came from MS because when I looked at the details it pointed me to this MS Security Bulletin. If you think it's always safe to get the updates from this pop up then I'll heed them from now on.