I have a 1T WD SATA drive in my ThinkCenter 8189F6u. I "think" it was working fine earlier but I'm not sure but now I know its very slow. HDTUNE reports that its running 3.5MB/s and robocopy showed similar results. Any ideas what the problem could be. I have an old SATA drive that I guess I should try swapping for that one just to see if its a drive problem.

Check the device settings, and look if it is running in PIO mode. It should run in (Ultra) DMA Mode.

How is your SATA Controller configured in your BIOS? AHCI / IDE ?