Yeah I was/am a bit concerned over a new noise that started happening with my Macbook Pro after installing the OWC optibay.
Got a SSD from OWC so I put the factory 750GB HDD into the optibay. Now, whenever I restart the computer when it was running Windows, it'll make a single tick sound when it starts to reload to BIOS. The click sound is coming from the HDD and I thought maybe it was failing even though it's a new drive, but I noticed it never makes that tick sound when I restart the computer from Mac OS, so I am just assuming it's okay since it never makes that noise any other time.