Thanks for the reply Dave.
When the power went off it was for a few minutes. Nothing in the house worked. When it came back on everything is working again except the computer which was doing the vista install.
I have a surge protector on the computer and modem, which didn't trip.
This leads me to think the power supply is still ok on the computer. The light is on the front, I can hear the fan running and it beeps constantly but nothing else is happening. The power button light is on the monitor but the screen is blank.
I am at a loss at what to do next, any help would be appreciated.