What cmos is, is a set of configurations so that the computer knows about some of the hardware and what to do that to get in to your OS (operating system... windows) If something got messed up in cmos your computer might not turn on correctly and you wont be able to load your OS. To make sure that your cmos isnt wierd you could check it, but you probably wont knowwhat to look for, or you can reset it. To do this you have to open up your computer. You have to look on your motherboard (the thing everything else connects to) for a jumper (a little plastic square with metal inside, when the metal touches two prongs on the motherboard or hard drive it makes a connection telling it to do something or be configured some way) There is a ceratin jumper you are looking for. Above the jumpers there are usually numbers like 1-2 or 2-1 somethin like that. Look around on your mother board for a spreadsheet looking thing that would say "1-2 - raid 1, 1-3 - raid 2, 2-1 - reset cmos" your looking for the number that resets the cmos (they mihgt lable it BIOS instead of cmos. Keep in mindtheat this chart will be very small and youll probably skip over it the first couple of looks. You might be able to look in your manual if you still have it. Once you find the jumper there will be three metal prongs. Two of them will have a jumper over them (to set the CMOS to normal) move the jumper one prong over (this sets it to reset the CMOS) Turn on your computer... it should stay black. Then turn it off and put the jumper back to where it was before. Hopefully that will fix your problem. If it dosnt you will need to provide more info... Ill send you a PM with my aim name.