Just bought 2 4GB sticks of DDR2 RAM, and they don't fit in my motherboard. The new sticks are Komputerbay 240 Pin 800MHz PC2-6400F DDR2 ECC Fully Buffered FB-DIMM Memory Modules (on the bottom in the picture), and my old sticks are Geil PC2-8500 DDR2-1066 Memory Modules (on the top in the picture). My motherboard is an ASRock N68C-GS4FX. My guess was that the new motherboard required non-ECC momory, but I really don't know. Thanks in advance, Will
It looks like you bought Fully Buffered DDR2, which is not compatible with DDR2 slots.
If you need further information, you can start with this Wikipedia article
240-pin DDR2 FB-DIMMs are notched differently from conventional 240-pin DDR2 DIMMs. As a result, those two DIMM types are neither mechanically nor electrically compatible.
If you somehow ended up with a boatload of the Fully Buffered DDR2 RAM (different architecture than standard DDR2) you might want to consider purchasing a used HP XW6400 Workstation Computer - around $100-$150 refurbished on eBay. They take the Fully Buffered ECC Memory and Max out at 16gb. Makes for a superfast desktop replacement PC, faster than anything I've seen new if you get one with a Quadcore.