As the title says, don't be the fool that ends up losing data because you were too lazy to make proper backups! As always, I highly recommend SyncBack Free for the job, since it's quite powerful for being 100% free. http://techgage.com/article/using_syncback_to_synchronize_your_windows_folders/
I had to do a restore from a backup the previous day because latest AMD driver messes with Lord of The Rings Online. No matter what I did, even removing it and using Driver Cleaner wouldn't do the trick, but rolling back to an earlier back up did. 280GB of space might be used up by backups, but I'm happy to set it aside if it minimizes downtime. 15 minutes to restore is easier than hours to reformat, reinstall the OS and then try to get everything back to how I had it. Like Rob said, backup your shit!
The Lord of the Rings Online 276.3 hrs / 913 hrs Are you sure it's not just a sign?!?! (I kid, I know you obviously leave it open 24/7, I do the same in an MMO).
Yeah, it's the launcher that Steam recognizes, not the actual game...or maybe I have a problem. *twitch, twitch*
Oddly, Defiance is the same way. I had 4 hours clocked in before I actually played the game, because you need the launcher to DL the game :S