You'll need to create and format a partition on the new drive using Disk Management before it can be accessed. Right click on My Computer and pick Manage, then pick Disk Management from the left hand tree list. The two drives (plus any opticals etc you have) will be displayed in the right hand pane. Once you've written the initial signature to the new drive it will appear as a bar of unallocated space, right click in there and pick New Partition, check the values are sensible in the pop up and check the Quick Format box. Once you hit OK it'll tak a minute or so to sort itself out but that should be it done. If you want you can swap the drive letters about so that the HDDs are C & D and any opticals start at E but that's personal preference.