There may very well be something hidden on the hard drive. I wouldn't be surprised as drive systems such as these are setup to be fairly automatic with regard to being used as backups via the manufacturer's software.
Were I you I would avoid using WD systems. Some are not well-suited to use with Macs while others are not compatible at all. Using these systems is not what you need for basic storage or for Time Machine backups. If you are even slightly mechanically inclined you might consider the following:
Basic Backup
Get an external Firewire or USB drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):
1.
Synchronize! Pro X (Commercial)
2.
Synk (Backup, Standard, or Pro)
3.
Deja Vu (Shareware)
4.
Carbon Copy Cloner (Donationware)
5.
SuperDuper! (Commercial)
6.
Intego Personal Backup (Commercial)
7.
Data Backup (Commercial)
8.
SilverKeeper 2.0 (Freeware)
9.
MimMac (Commercial)
10.
Tri-Backup (Commercial)
Visit
The XLab FAQs and read the FAQ on backup and restore. Also read
How to Back Up and Restore Your Files.
Although you can buy a complete FireWire or USB drive system, you can also put one together if you are so inclined. It's relatively easy and only requires a Phillips head screwdriver (typically.) You can purchase hard drives separately. This gives you an opportunity to shop for the best prices on a hard drive of your choice. Reliable brands include Seagate, Hitachi, Western Digital, Toshiba, and Fujitsu. You can find reviews and benchmarks on many drives at
Storage Review.
Enclosures for FireWire and USB are readily available. You can find only FireWire enclosures, only USB enclosures, and enclosures that feature multiple ports. I would stress getting enclosures that use the Oxford chipsets (911, 921, 922, for example.) You can find enclosures at places such as;
Cool Drives
OWC
WiebeTech
Firewire Direct
California Drives
NewEgg
All you need do is remove a case cover, mount the hard drive in the enclosure and connect the cables, then re-attach the case cover. Usually the only tool required is a small or medium Phillips screwdriver.