This can be done in bios. Press Del when the computer start up to get into bios. But (1) DONOT do this unless you know what you are doing, read your computer's manual. (2) Some motherboard maynot have the capability to change memory's CAS. (3) If you cannot change CAS latency from Bios, the momory maynot be good enough. Get one stick which is compitable with your motherboard. If you buy from Crucil click here, you can chose one from their website which is compitable with your motherboard, read manual to find out info about your motherbboard.