[Memory] Installation Issues

[Hica]

Last night I installed two 1GB sticks of 184 pin DDR 400 RAM into my ECS NFORCE4 a939 motherboard. Prior to installing the new RAM I had two 512MB sticks. At first, I tried to just add the two new sticks to the two empty memory slots, but the memory didn't fit. I took the old memory out of their locations and replaced it with the two new sticks. The old RAM didn't fit into the other two slots either. I'm not sure what the significance of this is, but the four memory slots are color coded: the two memory slots that are working for me are blue, and the two that aren't are purple. After installing the two 1GB sticks into the slots vacated by the old memory, I booted up my system, checked Properties under My Computer, and it still says I only have one GB of memory.

What could be causing this, and what's up with certain memory slots only accepting sticks of RAM? I apologize if the information I'm looking for can be found in the FAQ, I couldn't find it. My system specs are posted below, thanks in advance for the help everyone.

Windows XP 32
AMD 3500+
ECS NFORCE4 a939 (http://www.newegg.com/product/product.aspx?Item=N82E16813135177)
Sound Blaster Audigy 4
EVGA GeForce 9800 GTX 512MB
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231039 (the memory I purchased)

 

[Mondoman]

If the DIMMs won't fit, you've either got the wrong type of DIMM, or you're not installing the DIMMs properly. I suspect the latter, as all 4 slots should be the same on your board, and sometimes with the tight clearances, it's hard to get those DIMMs inserted exactly straight. If they're not put in exactly straight, they "won't fit".
What are the model numbers (not just names) of both your 2x512MB DIMMs, and of the 2 new 1MB DIMMs?

 

[Hica]

I'm not sure if this is exactly what you're looking for, but here goes:

1GB: F1-3200PHU2-2GBNT

512MB: PSD1G400KH

 

[Mondoman]

All your RAM modules are spec'd higher than the DDR standard 2.5V; try setting the RAM/DIMM voltage to 2.7V in the BIOS. Unless you're wrong on the MB model, all the DIMMs should physically fit.

 

[Hica]

I took all of my RAM out and inserted the two 1GB sticks into the slots and now it recognizes that I have 2GB's of RAM. However, when I insert the two 512MB sticks into the remaining slots and power on my PC, my system freezes at the very first screen (says my system specs, etc).

At this point I'm just happy that I got the two new RAM sticks to work, but I'm curious as to why my system freezes with all four slots filled. Thanks for everything so far!

 

[Mondoman]

Remember that just because the system booted doesn't necessarily mean the RAM is working without errors. Download the free memtest86+ bootable CD image and burn a CD with it, then boot from that. Let it run O/N to make sure you don't have any obvious memory errors.