Norton Anti Virus 2005 does not support repair feature. Please uninstall & reinstall

I have just purchased a new virginal computer (running Win XP home). It had a pre installed 90 day free trial of Norton Internet Security, so I thought I would give it a go. I assumed that by registering it would flick a switch and fire up. In fact it then spent most of the day downloading relevant components from the internet. As frustrating as it was, in the end it seemed to work.
I then decided in my wisdom to remove all the computers AOL stuff which I had no intention of using - I did this via Control Panel / Add or Remove programs. That also seemed to work.
Since then though I keep getting the message in the above title (multiple times). I assume it is from Norton Security but am unsure. I dont want to uninstall that without knowing how to get it back (as I have no CD), and I dont want to spend another day downloading.
Does anyone know the reason for this message and more importantly, how to recover from it?
Is it likely that I have removed common files, if so can they be recovered?
Is it Norton that is meant to be reinstalled or part of Win XP?
Thanks
Dave
It would have been nice to ask Norton but all you get are FAQ and no way in which to communicate other than very expensive calls - it might influence my decision whether to purchase the product when the 90 days is up!