1. do you know how to image your OS?
use Acronis or Norton Ghost..the easiest and most effective way of making a backup of your drive/OS...you only need to restore your created image even if maguba pa na imu OS.
2. dont worry about files...kung na save imu files sa lain na drive like drive D or E, dili ra na mawala..all you have to do is to reinstall your OS without touching the other drives like D / E..