Problem with EPOX 8RDA3i and Athlon XP T-Bred 1800+

Hey there.
I have a huge problem and I was hoping you could help me.

Originally, I had my Athlon XP 1800+ (T-Bred, 1533 Mhz) on an EPOX 8K9A (Via KT400) motherboard. Having bought a better EPOX 8RDA3i (nFORCE 2 Ultra 400) motherboard, I moved the CPU from my old board to this new one, but got the following problems:

1) The system won't pass the POST (No signal on the monitor, the display from my motherboard shows FF, then stops at 25, followed by a error signal - like an ambulance sound... from my experience, that problem sounds like a CPU error). I removed my VGA card, nothing changed. Removed the RAM, the system saw that it has no RAM and beeped.
2) I moved back my CPU to my old card, but my Windows XP (SP2) won't start (it stops before showing the Windows XP Logo, and in Safe Mode it stops when loading Mup.Sys).
3) I installed another similar, tested and working Athlon XP 1800+ on the 8RDA3I and nothing was changed.

What could be the SOLUTION?????
My CPU is fine, no pins are bent, nothing is wrong...

Could you help me, please?

In the beginning I connected only the 20-pins to the motherboard and got code 25. Then I connected the additional 4-pins and then the system wouldn't start. Strange, I said. Stranger - I could place those pins in any position and they still fitted. But the system just didn't start.

Then I saw that those pins were different from my old PSU (a regular no-name 400W), having voltage on all 4 of them... I remember that only 2 of them are supposed to be "fired up", the other 2 are GROUND... am I right?

All of that outside my chassis.

I found out on my own that 25 is a code that comes AFTER Video card detection... I tested it with SEVERAL (and I really mean SEVERAL) video cards... could this be a problem with the AGP port?

Thank you. :bowdown: