Yea you can run faster ram in a slower motherboard, they are backward compatible. The RAM will not be fully utilized as it will not be running at its full speed or OCed, but I don't think you should have any problems.
I was wondering if the A7N266 had a locked PCI, this is an nForce(1) motherboard, and I heard somewhere that their PCI WAS locked, not sure about it tho. If its true, you can get the faster RAM and do some serious FSB OCing w/o worrying about HD corruption or PCI cards failing