If you install Windows on a drive that already has it installed you will see a Windows.old file on the C: drive. The older install with it settings should be in there. But you may have to pull out files and registry keys, etc to get programs to be working, unless it is pictures and such that you want to back up.
But to be on the safe side, get a cheap USB-drive or something to back it up to, as someone stated earlier, drives will always fail at one time, it is just a matter of time, and luck.
If you, like me, have a second drive, put them there. I have one for games and such, and not Windows, as it is on my SSD. The second drive, where the OS is not going to be installed is not touched.