I have recently aquired a Gateway 700gr - p4 550 3.4ghz 1g ddr sata.
The machine will not post. Fans come on but nothing beyond that. I have tried removing the peripheral cards one at a time and nothing. The only reaction I get from the machine is when I remove both sticks of ram it gives me the 3 beeps signifying ram issues. I have replaced the ram with known good ram and still no reaction. Have also replaced the psu. Still nothing. With the lack of btx boards out there, I am at a standstill on how to proceed with troubleshooting this. I have also tried resetting the cmos.

Any help would be greatly appreciated.

This sort of post puzzles me. If it's a recently purchased new Gateway system why isn't it going to Gateway for warranty attention?

If you're intent on doing it yourself, the troubleshooting procedures in the pinned topic at top of section still apply. Get it working in 'barebones' configuration first before adding back in any cards, drives etc.

The machine is out of warranty.....as for the "barebones" approach, I have had the machine down to the minimal parts required for posting and still nothing.

Then it is either motherboard, processor, power supply unit or a faulty RAM module. You can get a technician to test it or you can borrow suitable spare componnents from elsewhere for testing purposes. There's basically no other way to tell which is the problem.

Put it this way, if you have the basic components, they are compatible with each other and connected correctly, and it doesn't POST, then one of them is non-functional.