One suggestion from Microsoft is to try the diskpart command to see if the drive shows up.
"1. Type diskpart, and then press ENTER to open the diskpart tool.
2. Type list disk, and then press ENTER. A list of available hard disks is displayed.
3. Type select disk=[n]
n specifies the disk number of the disk to receive focus.
4. Type list partition
This command displays the partitions listed in the partition table of the current disk.
5. Type select partition=[d]
This command selects the specified partition and gives it focus.
d specifies the drive letter or mount point path of the partition to receive the focus.
6. Type format drive: /fs:ntfs /quick
For details on the commands, refer A Description of the Diskpart Command-Line Utility
http://support.microsoft.com/kb/300415"
Source:
http://answers.microsoft.com/en-us/windows/forum/windows_vista-hardware/2nd-hard-drive-not-showing-up-in-my-computer/2d73e570-a007-46d5-aaee-9d1cbe915813
I'm not sure whether or not this will help -
http://knowledge.seagate.com/articles/en_US/FAQ/168595en - but it may be worth a read. It address a drive not showing up in the BIOS. The trick here is whether or not the drive needs to enabled in the BIOS. Since yours is set to automatically detect drives this may not apply.
Have you checked to see if a BIOS update is available?