its840, I'm guessing you tried to use some sort of recovery program. My suggestion to you is to make frequent back ups of your computer. a 300gig (external) drive can be had for 150 and I'll get you Norton Ghost
Let the image thing run over night and you have a complete back up of you system. If your kids crash it, the back up should be an almost direct replacement.
The Maxtor one touch back up software, lets you either use their program to "restore" your stuff or it basicly coppies ALL the files onto the backup hard drive so you can literally boot the computer off of it.