's free version and run the error scan every three to six months or if you think you are having a drive problem. On its Health tab, the key item is the Reallocated Sector Count. Modern drives are supposed to fix themselves and will indicate they are failing when the reallocated count stops being 0. The error scan will show you any "bad sectors" which should not exist.
If it is caught early, simply cloning the failing drive to a replacement will fix things (I do a lot of data recovery and this is what works about 80% of the time)
Karen's Replicator will automatically update the destination folder on a schedule you choose. My E-Mail, Documents, Favorites, Pictures, Music, and videos get backed up every night across the network to another computer. It has been almost 20 years since I saw a thunderstorm blow every computer on a network so the graetest danger is a fire or theft. The note is; though, that it is the separate circuit breaker and power supply which makes this much more secure than an external drive or a second internal.
To answer one of your questions; no, generally you will have to boot a CD to clone the OS drive. I don't even bother to do this; but, if you so desire, I would only do it after a clean setup, after any major software changes, or about once a year.
Since it seems as though you had a drive or two crash, I will add this; Seagate and Hitachi make the best drives, followed by Samsung. Maxtor and Western Digital make the worst (they account for 75+% of my data recoveries)