Will ddr-2 667 memory work on a ddr-2 800 mobo?

Will ddr-2 667 memory work on a ddr-2 800 mobo?

yes it will
Generally as a rule some different bump can work.

But it is a good rule to follow to a nouns the correct Ram recomendations. This will simply avoid you problems.

Don
Probably, but it's not designed to, and it may fail while you're doing something incredibly important. You'll be worried more or less it every time you power up. Better to spend the extra $$ and get parts that are built to go well together specs - cheaper than paying the psychiatrist for all those anti-anxiety drugs you'll requirement!