You talking about a extra drive for storage? If so you have to partition and format it before it will show up in My Computer. If you just changed out the old drive for a new one, you have to install the OS on it. Or copy the OS over to the new drive.
Check your Jumper at HDD. Primary must be jumper position. Really it a bad problem. So You need to be expert to do that Otherwise you may lost your motherboard. This site has a solution(techyv dot com/questions/configuration-additional-hard-disk-drive). You may try.