I took delivery of a WD MyBook Dual Drive this morning and though I don't usually write reviews I was moved to do so this time. I was almost put off by the feedback on this site and I don't want anyone else to be.
The drive is way smaller than I thought, it looks great on my desk and it is a quiet as a mouse. It's certainly quieter than my high-end Samsung laptop. It came with all 3 cables (firewire 800, 400 and USB) and was a doddle to set up in XP. I reformatted it from RAID 0 (the default) to RAID 1 in about 10 seconds. I copied a 500MB video file across from my laptop using USB2 in less than 30 seconds and it is playing back off the drive smoothly as we speak.
I think the complaints about noise come from the fact that the unit appears to have a 2-stage fan. For about 2 seconds after you start it up and once for a couple of seconds while I was formatting it the second stage fan came on and it is quite loud. No where near the hair dryer levels mentioned in other reviews but certainly a bit louder than your average desktop fan. But I've been using this drive now, streaming video from it continuously, for well over an hour and the second stage fan has not kicked in at all. In fact if you leave the drive idle for any length of time it goes into sleep mode and the fan cuts off completely - making it totally silent.
So my advice is, if you want 500GB of secure RAID storage at a decent price don't even think twice before getting this drive. It's not noisy, it works perfectly and it looks great. And it's top value too. In fact it's so good I might even buy it's sister the network-capable world edition to replace my ageing (but very reliable) Iomega network drive.
And before you ask I have absolutely no association with WD or anyone who might benefit from sales of this drive - I just wanted any potential buyer to know it's a genuinely great piece of kit.