Vista Ultimate - Problem with Auto Updates

Hi all

I've just got a brand new computer with OEM Vista Ultimate pre-loaded, and
cannot get autoupdate to work. It I think downloads files, but doesn't
install anything, instead, gives me error code C015001A.

Because Vista is relatively new to me, I'm not sure about the security
features contained within, but I know my account is set to administrator.

I did think of re-building myself, but I don't want to do that if I can help
it, plus it may not solve this problem.

I've tried review the WindowsUpdate.log, but it's doesn't mean much to
me.....

Any help much appreciated.

Thanks, Mike