Question: will ddr2 800 work in 667?
Answer: So yes, you can put 800mhz memory in your machine, but unless you overclock it, it will run at 667mhz. You won't be able to tell any difference in speed even if you do overclock it and set to run at 800mhz. But, there is no reason not to buy 800mhz memory if you have found a set at a good price, it will work fine.