1.0TB Hard Drive Drive Letter?

I have a 1.0TB Hard drive as a secondary drive to store videos from my surveillance system. It is stored under drive letter S:\. I go to "Create and format hard drive partitions" under "control panel". Then i go to "Change Drive Letter and Paths". Then "Add". Then change it to drive letter S:\. Everything will go fine until I turn off my computer then when i reboot, the 1.0TB hard drive will not have a drive letter and I have to repeat the process over and over. Both drives are healthy. Both also say active, primary partitions. My C:\ drive also says system, boot, etc. My motherboard and OS (windows 7 32-bit) support the 1.0 TB hard drive. I need to get the hard drive to keep its Drive Letter, even after reboot. I can see the hard drive on "My Computer" and then when it reboots its gone again. I have tried assigning it to different drive letters so that is not the problem. Under the BIOS i was able to set up the drive with no problem and the drive shows up every time whenever i try assigning it to a letter. Any suggestions will help