I've got an hdd in a hot swap bay and,of course it shows in "safely remove hardware."
But it also lists an internal hdd.
OK, first confusion:
The st31000526sv is a Seagate part number. Probably an external drive.
Western Digital drives start with WDC. So I think you are talking about 2 different hard drives here.
The symptom of internal hard drives showing up as removable is usually caused when you are using the generic AHCI driver that is supplied by Windows 7 Installation. This is a very basic driver, just enough to get systems up and running.
The symptom is usually solved by installing the motherboard manufacturer's dedicated AHCI driver. This should be available in the Downloads section for your motherboard.
The symptom can also be solved by installing the Intel Rapid Storage Technology Driver (IRST). But you must be sure to use the correct IRST for your system. This is usually also included in the Downloads page.
We can see better what is going on with your hard disks if you can post a screenshot of your Disk Management Window, expanded so all information is visible.