Basically, you need to go into start > all programs > administrative tools (or start > all progs > accessories > administrative tools, depending on your setup). Next choose 'computer management' and within this 'disk management'. Here you should see your existing hard disk, plus your new one represented as 'unformatted space' or something similar.
Right-clicking on the new disk will provide some options (i can't remember what exactly) that allow you to initialise, partition and eventually format the disk. Having done all this you should see your new disk in 'my computer'
Before you do all that though you might want to change the drive letter of your cd drive to push it further down the alphabet, so to speak. For example if your cd drive is D:\ you might want to make it E:\ so that your new hard disk can be D. You can do this from the disk management window too.
Hope this helps..