I recently purchased a MBWEII 1 TB model from a co-worker on the cheap (it was already out of warranty). I received only the unit, ethernet cable, and a power supply, but everything worked properly when I set it up at home.
Being a moron with just enough Linux experience to be able to screw things up consistently, I figured I would upgrade it to a 1.5 TB NAS using the 2 Seagate Barracuda 750 GB drives I had laying around. Thanks to the assistance offered by this site, and specifically to some useful posts by christoff4444 (http://mybookworld.wikidot.com/forum/t-48373/backup-images-for-wd-mybook-we-ii-2tb#post-130623) and ETMegabyte (http://mybookworld.wikidot.com/forum/t-48373/backup-images-for-wd-mybook-we-ii-2tb#post-199958), I loaded up a Knoppix live dvd and ran through the recovery procedure described by christoff4444 with no apparent issues.
When I connected the two 750s and plugged in the device, I could hear one of them spin up properly, while the other one started to spin up, then issued a click and started over repeatedly. I tried removing one drive at a time and plugging each into both bays in the MBEWII; both drives spin up properly on their own.
I know that these drives are both functioning properly outside of the MBWEII, so I am forced to assume at this point that the spin up power requirements aren't being met by the power supply that was given to me. Does anyone have the power supply specs for the brick that is shipped with this NAS? The one that I have seems kind of fishy, as it looks like a cheap Chinese PS, and it is only rated at 12V/2.16 A. On the Western Digital site, the description for the replacement power supply says "48 Watts" (http://www.westerndigital.com/en/products/accessories.asp?ProdID=176), so I'm pretty sure mine is not the correct power supply. Can anyone offer any wisdom?