just go swap/sell the stick of ram for a stick of the correct frequency. I wouldnt want to risk saying to you anything... however i do know that my old pc mb was only rated for pc266 and i used pc333 for a couple of weeks... but i wouldnt recomend it
It should still work, even with a voltage difference of .1v. .1v is not enough to cause it not too work. Average threshold variance is .3v I belive. Worse case it won't work or refuse to see the RAM board. Won't hurt anything either way.