Normally it is possible to put any 2.5" S-ATA HDD with a maximum height of 12.5 mm in a Unibody MacBook, but maybe that HDD has a propriety connector WD put on there.
Can you make a photo of that HDD's connector and attach it to your next post?
MacBook, MacBook Pro: Replacing the Hard Disk Drive, transferring data to the new HDD
the guide includes:
- 0. Identify your MacBook or MacBook Pro
- 1. Getting a new HDD
- 2. Guides to replace the internal HDD with a newer one
- 3. Transferring data from the old HDD to the new HDD
- 4. Using the optical disk drive (ODD) slot for placing an SSD or HDD inside the MB/P (OPTIBAY)
That's not a standard SATA interface. Where did you get the drive?
Yes some use standard SATA drives. Best bet just to buy a bare SATA drive.