Vista Upgrade Blank Screen

Hello,

Dell Inspirion 1505S Upgraded to Vista. Wireless cared failed. Tried Belkan Wireless card. PC accepted "upgrade". Then notified me of updates (mid August 2008). I authorized the updates. The computer rebooted. Now it will not boot at all. Power lights come on for 2-3 seconds then go dark. I called Dell. Warranty expired.... but a tech retold me it was likely a motherboard failure. I question that as it failed immediately after/during Vista update. They told me to hold the Fn key down and power up. No change. Initiallly I would get 1 light on and two flicker. But the end was the same, it powers down. Nothing an the screen. I dissembled it and cleaned the contacts of the various components. (reassembled it, I had experience with this on the Inspirion as my daughter has one and I have had to replace several components ...rough handling...) No overt damage noted. No change. Any ideas..... Thank you