Can't mirror to a WD Black 500Gb

I have a customer who has two drives in a MS Mirror RAID 1 array. One drive went down so I purchased a WD Black 500Gb to replace the drive that went down. However, Windows (Server 2008) reports that all the drives must have the same sector size.

I did some rough calculations and found that the WD Black should have 512-byte sectors, the same as the existing drives (Seagate ST3500418AS), according to their web site, so it should work.

am I missing something obvious (or not so obviousl)?

Thanks

PS: I forgot to add the model number of the WD drive. It is a WD5003AZEX. Also after another think about this, I’m guessing that the drive may be 4K/sector but reporting as 512Byte/sector, and the specification sheet is showing the “reported” sector count, not the qactual.
If this is the case then I’m a little surprised that a “small” 500Gb drive would be formatted with 4K sectors. Also I’m really frustrated that WD don’t give the actual sector size on their site anywhere, as this is part of the basic information that we need to know, particularly when we are trying to replace drives in a RAID that doesn’t like mixing and matching sector sizes! If the information is there then this information is hidden away somewhere non-obvious.

In the end I had to abandon the attempt and clone the existing drive to the WD drive, then use that as the master drive and add another WD drive so we could mirror to that new one.

Shame that WD seems to think that sector size is so unimportant that they don’t even put it on their spec sheet!