Don't forget that a good backup strategy starts close to home. In other words, if you have any material that you value on your PC, you should really make sure that you've got it securely backed up (for example, if you have a static copy of a site, or business documents, or family photos - anything that you'd kick yourself for losing)
That could include:
- A local backup to a hard drive physically attached to the machine (internal or external, doesn't really matter). Simple, but has several disadvantages: if your machine gets stolen, the thief may pinch the peripherals too. If your house floods, burns down etc. then everything's in the same room so is likely to suffer equally. If you get one of those nasty ransomware viruses, it might encrypt EVERY hard drive it can find. And so on.
- A networked backup: hide a drive somewhere else in the house, and backup to that. Suffers some of the flaws of the local backup, but a better bet for thieves and possibly more secure from viruses if you practice good security
- A remote "sneakernet" backup: periodically burn your data to portable media (Blu-ray, USB stick, portable HDD etc.) and stash it "off site" i.e. somewhere other than your home. Protects against theft, is unlikely to get damaged at the same time as your machine - but may not be particularly up to date if you don't do it very regularly
- A remote "cloud" backup: send your data into the "cloud" through a service like Mozy, Crashplan, Backblaze etc. Has similar advantages to sneakernet, but at a monthly fee and with a possibility that the cloud might get "hacked"
Personally, I practice a mix of several of the above as I've got tens of thousands of documents going back to the mid-1990s, plus over 100,000 photos and videos, and it's almost unimaginable losing the lot for the sake of a couple of extra drives and a few quid a month in backup service provider fees.