Change your mode in the bios for the Sata ports from, Sata mode, or Raid mode
To AHCI mode for the drive you wish to install windows on. Depending on what Sata port it is connected to on the motherboard.
Save the new setting before you exit your bios.
When you get to the windows install and setup where it asks you what drive you wish to install windows to.
You will see the new HDD listed.
If the mode set for the Sata ports is set to Sata mode in your bios, and you wish not to change it.
Follow this guide to get the drive to show in windows setup and install for the target drive for windows 7 to install to from the DVD disk.
When installing windows.
On the page where you are asked where you want to install windows to.
Look to...