Provided the drive is not formatted as a dynamic type (a look at the drive(s) in administrative tools will tell) a FREE program called Easeus Todo will do the job nicely, planting a complete copy of the C: drive/partition on the extrenal backup drive. Takes less than 30 min to do the backup, then if disaster strikes, about the same to reload the entire system as it was when you saved it, as opposed to an hour or so to reload windows and a week or so to update it and get all your programs and settings back. The same firm also do a very good partition manager, so you can create and adjust the size of the pretend discs that live on the same actual disc.
As someone said recently, if you dont have two copies of your data in different places, you didn't really value it in the first place.
Keeping files backed up is easier using MS's freebie "synctoy". After you've got the folders copied, you just use Synctoy to pair those in the PC with those in the external drive, and run it. The newest copy wins, both ways. Simple, cheap, easy and effective.
Shopping around a bit, about £80 for 1TB is the going rate, give or take.