My updates are being blocked

I have just taken delivery on a new computer with windows vista, when i try
to close the system down it will not close down after leaving it for ant
length of time. I suspect its trying to download updates from microsoft but
for some reason it bappears these are being blocked. This has also happed
with other applications i have tried to down load from the internet. Your
possible solutions to this problem would be appreciated.

Thanks
--
Dex