DDR400 in DDR 333's place?

hey guys..
My mobo is an intel D845GVSR ,ram's 200/266/333 MHz Non-ECC unbuffered DDR SDRAM..i bought two DDR400 Mhz 512 MB rams because i thought thaey wud be downward compatible.The trouble is that the 400mhz rams don't work alone or in combo,but if one 400 is coupled wid my old 266mhz ram then it works & i get 768 MB at 266 mhz.

IS there ne way that i can get both the 400Mz 512 MB ram modules to work together?
pls help.....

I think your motherboard cant support 400mhz DDr ram, though if it is put with the prior ram it will give only 266mhz as you said. :no:

You can add the 1x512 DDR400 but it will not run dual and the DDR400 will automatically set to that of DDR333 if not then do so for stability. So all the rams should run at DDR333. It will slow it down at bit since it does not run dual anymore but with high application more ram is better.

I'd recommend getting 333 to begin with, because the computer will tend to have compatibility issues in my experience with some 400mhz models. Haven't looked at prices lately, but I would assume it would also be cheaper as well. Regardless, the speed will be limited to 333 on that machine.

thanx guys......
the trouble is that333's a lot rarer now & costlier too than a 400....but i was thinking can a BIOS upgrade do the trick?