A quick check will tell you if Windows see's your drive (but still won't be visible to My Computer). Right click My Computer, select properties. At this point you should have the System Properties window open. Select the Hardware tab and click the Device Manager button. Click on the plus sign next to Disk Drives to expand it. If both your HDD's show up here, then proceed to the next paragraph. If it doesn't, it means that your SATA driver isn't installed.
You need to partition that drive before it will show up in My Computer. To do this go into Control Panel and then Administrative Tools. Once in Administrative Tools launch Computer Management and you'll see under Storage, Disk Management, click it. At this point, you should see your second drive most likely labelled Disk 1 in the lower righthand pane. Right click it and choose Make Partition. I imagine that you'll want to use the entire space as one partition. Once the partition is made, you should be able to see it in My Computer. You can choose to format from within Disk Management by using the same procedure I described above for making the partition. Right click on your partition and select format, pick you format type (most likely NTFS) and let it rip. Hope that helps.