pob

I am about to pruchase a 256 Mb ddr for a 845 board i have. I already have a 256 Mb ram (ddr) running a 333 Mhz. I want to add another 256Mb in another slot. Even if i buy of 400Mhz it will be underclocked to 333 Mhz so thats not a pob. What i wanted to know is whether i have to take of the ram...