Dell System Updates- BIOS- Wiped ALL of my files

After putting it off for a couple weeks, I finally did my Dell system update which was supposedly a Bios update.  Upon restarting, ALL of my files were wiped (except the ones in my recycle bin- go figure!). I have Carbonite so I am restoring everything but it takes a long time and is very frustrating.  I wanted to put this here as a warning to anyone.  How could this have happened and how can I prevent it in the future, besides not doing any updates?