I decided to upgrade the memory on my desktop from 500mb to 2gb (DDR) the old memory was 266MHz and the new is 400MHz which my motherboard manual says is OK (M7NCD). The memory seems to be working OK but the computer tells me that I have 2GB 266MHz, should I have changed any settings or should I leave well alone. ::)
If bios is set to auto for CPU and memory. I would hope a CMOS clear would allow the new memory to be reconised.
Otherwise you will have to dig deeper into bios to look at memory speeds in relation to the bus speed (FSB).
If you have mixed old and new memory I believe they will run only as fast as the slowest