Vista - Problem Installing SP1 (Vista Home Prem) - Hangs on faze 3

I have received SP1 this morning via Windows Update.
It started to install and asked to reboot to finish install.
I went to lunch and after several hours is still doing this:

Show a message in the screen
Installing Service Pack: fase1 of 3 0% completed
After more less a minute it says Shutting Down and reboots

When it restarts it shows the above message again...
Time after time, it's been doing this for the last 5 hours!

Can anyone help??

(Please apologize if the English is to perfect. English is not my first
language)