Hi superstar, one of the best options you can have - especially if you're looking to buy stuff - is to purchase a backup hard drive and use it to copy all your stuff. If you want to purchase a program also, I recommend using Acronis True Image, this will make an exact duplicate of everything on your hard drive. So if your drive fails, all you need to do is put in the new hard drive in your computer and then you can load the Acronis program and it will just put everything straight back on like it was the last time you did a backup. You won't need to install Windows again or anything.
You could also purchase another hard drive (exactly the same one as you already have) and use RAID 1 (mirroring).
The only way you can tell if your hard drive is going to fail is if the SMART warning comes up, even then it usually doesn't predict it anyway. My horror story is that one morning my computer just would not start. The POST almost finished loading and gave me an HDD error, I could hear this horrible ticking noise. It was a mechanical failure and the whole lot was gone in an instant. I had to get a whole new hard drive and start again - I actually got two, one for backups. I learnt my lesson!
I strongly suggest you be PROACTIVE and get copies of your data everywhere (not just on the backup drive, but on DVD's every now and again) so that you won't lose it.