memory expansion

ive recently expanded my 128mb RAM by a DIMM of 256mb, when i enter the cmos(bios) i can see TOTAL mem: 384mb, and then i see next to the old 128 memory (PC133) which i guess its okay, and then i see next to the new 256, (Not SPD). As you might have guessed i dont know a lot of computers, does anyone knows what does the Not SPD message stands for?, is that OK? thanks a lot