mixing memory issue 667Mhz and 800Mhz

Hi,

My desktop is a HP XW4400, having 2x512MB Dual of RAM preinstalled.
Each 512 (Hyundai Electronics) is: PC2-5300 667MHz ECC.

I just bought 2x1GB Geil RAM PC2-6400 800MHz, noECC.
Problem is that the new memory alone works fine, but I want to use all3GB and that's a problem. When I start the desktop it starts beeping (3 beeps once - pause - 3 beeps... )
What to do?

Thanks,

[/img]The memories work fine on their own .
So the 2x512 work fine and the 2x1G work fine. I used memtest86 Plus for this.

I tried all possible DIMM combination (DUAL and NON-Dual) and everytime I pair the 512 with 1G the beeping appears and nothing can be done.

The BIOS is stupid enough to be very simple and has no ECC disable/enable settings. The motherboard has no specifications and I can only learn it's HP model 06A68h which means nothing and cannot find any documentation related.

I don't know if I can do anything at this point rather than to throw away the 512 DIMMs or try sell it (which would be a fair price ? )

Andrei.

That might be the best. The problem with selling ECC, but unbuffered, DIMMs is that there is not a very big market for them. Standard 1GB DIMMs sell for around $40-50 each these days, so if you could sell your ECC 512MB DIMMs for $10 each, I think you would be lucky.