ADVICE on how to backup internal hard drive inside the HUB

Now we all know that all hard drives will fail eventually so I lost a small collection of movies and tv shows a year ago because they were on an external hard drive on my pc and HD crashed so I lost all my movies. After hours of crying I decided to always backup my files. So my question to the forum is what is the best / most efficent way of backing up the internal harddrive in the WD TV LIVE HUB. I mean I know I can just connect a 1TB HD to the hub but then to select files and how will I know what is backed up or not. Ideally I would like to somehow automate the backup so it backs up only new files. The hub is now my media centre and I do not have the movies anywhere else. This is why I want to back it up. ALso what happens if the internal hard drive does crash? how can it be replaced?

My Setup:

WD TV LIVE hub with a wireless adapter connected to my PC through my wifi. This is how I just transfer files from my pc to my hub. Under my network it pops up as a hard drive and i just drag and drop my files onto the hub.

Thx in advance

Hmm… I think the easiest would be to just buy a NAS that runs RAID… And hook it up to the hub and play from it…

Then it would take backup automatically (as the RAID mirrors the HHD).