Computer Randomly Restarts and Bios resets to factory defaults please

I was just wondering if anyone has an idea what might be causing my problem. The computer is is a dual xeon with windows server 2003. Randomly since about September/October it has reset itself and seems to lose the boot order sequence. I flashed it some time in November and it lasted 2 months without reboot/reset. I tested the battery and it was strong. I ordered a new bios chip thinking maybe it was faulty but now 2 weeks later it has the same result of the computer resetting itself and bios losing settings. Since then I have replaced the motherboard with an identical motherboard and it did the same thing again. My next step will be to replace the power suppply. Does anyone thinks this could be a software error or someone hacking the server. The Reboot reset happens randomly it could be 2 days, or 2 weeks or 2 months. Thanks.