Purchased a used compaq S5300NX desktop with monitor,keyboard,mouse, and other devices.First thing I did,was hookup the tower to my monitor,keyboard,mouse and internet connection. turned it on and it booted up fine and opened windows xp.I started checking files and discovered anti-virus protection was outdated and last update from windows or microsoft was 6 months ago.first I downloaded anti-virus software,then I downloaded microsoft and windows updates and updated service pack 2 to service pack 3.previous owner was still using internet explorer 6 so upgraded that to explorer 8.Then I shut it down and unplugged everything and pulled side cover off to see how dusty it was inside.I don't know how it was running,because of all the dirt and dust inside fans,optical drives,power supply and motherboard.After giving it a good cleaning with compressed air and vacumn,I replaced cover and hooked up monitor,keyboard,and mouse that came with it.When I hit power button the only thing that powered up are cpu and psu fans.Have solid green led on front and amber hard drive led stays on solid for only 2 minutes.Turned on monitor and it ghave green led for about 5 seconds then turns amber with black screen.Keyboard also has no power lights coming on but optical mouse has power. Swapped monitor with my old pc and it works fine.Hooked up harddrive in my old pc and itbooted right up showing all the updates that I had just downloaded,so I know it's ok.Reseated memory sticks,checked all connectors,and checked voltage from psu with fans running.All pins on atx connectors showed from 1-2 vol;ts under specs and on molex connections also.is my psu gone bad. Please help this old shade tree mechanic,if you can.Thanks