I put together my first AMD system 3 days ago: It's an Athlon XP 1800, Soyo Dragon Plus, Radeon 8500, Antec 1040, Antec 400W PS, crucial ddr, pal8045
I had some trouble initially with getting it to work. Whenever I hit the power button the case/cpu fans would spin for a second before stopping. No beeps or any other activity. Eventually i got it to work outside the case and replaced it carefully and got everything to work, installed win XP and all my other software.
Today, I'm working in my case changing an IDE cable and when I'm done and try to boot up I get the same problem. The fans spin for 1 second and then die. The only thing on is the green light on the MB and the LAN port. I tried everything i can think of, from taking the MB out of the case, removing all PCI/IDE devices, trying different RAM sticks, reseating the radeon card, checking the fans plugged into cpufan1, holding insert on boot, etc. I dont even know what part is broken so that i can return it and my old system is too archaic to be of any use in troubleshooting.
Kinda sounds like maybe a shorted circuit some where in a power lead or on the MB itself, maybe through a supporting screw. But you said you took it out of the case and ran it on the desk and still got it. Do you have another HS fan to replace the current fan with? Maybe that item is shorted inside? A previous poster and many others have had some difficulty getting no overspill onto the CPU from the thermal gel squeezing out, especially the conductive types like Artic Silver and others with metals in them. These are just some ideas maybe that can give you a direction, I know, I have been there many times over the years.
Good Luck, Take-Out
"We killed OUR Hitler" - attributed to Paul McCartney (If so, then well done, sir)
Try holding the Insert button in on the keyboard while turning the power on for the system. It should bring you to the bios setup screen. I was having the same problem when I set mine up last week. You may have to tweak some settings to get a stable boot up.
Athlon XP 1700
Geforce 3 ti200
256 MB Corsair 2400