Here, burn this principle into your brain: "There are two kinds of hard drives: Those that have failed, and those that will fail". Now that you are properly paranoid about losing all your hard work, feel free you use at least three methods to preserve it:
1. External hard drives.
Just copy the whole thing to another external hard drive and tuck it into a cupboard. But here is my horror story with that one: The main external drive fried (literally--there was smoke), so I confidently reached into the cupboard and pulled out the backup. That one wouldn't mount. Double whammy. So it is a useful method, but on its own it is not good enough.
You can also use an external hard drive for automatic backups, like Time Machine on a Mac. This makes your files immediately available, but there is still the inevitable fate of that drive to consider.
2. Burn to disc.
Can be a lot of work, and doesn't hold much video, but a DVD-r can't crash and they are easy to store. For the most important files, I like to put a copies in a firebox and/or store them off-site. Video can be burned to a playable DVD for backup. Yes, it is now compressed and not as sharp as the raw files, but at least it will survive the coming hard drive apocalypse.
3. Cloud storage.
I use Backblaze, and there are plenty of other option available (Anyone try Amazon Cloud Storage?). There are so many good things about this method. It is automatic, so you don't have to think about it. Files are preserved no matter what disaster may occur. It also doubles as a remote access to your files. If you find yourself on another computer but need a file from your main drive, you can download that file from the cloud for free. This has been a handy feature for me on many occasions.
By the way, if a hard drive won't mount, there is software that can recover the data. I successfully used Data Rescue for the disaster noted above. This was a whole lot cheaper than having it done at a repair shop.
