Comment by firefax

I'd suggest burning her a Knoppix CD-R. I learned on Knoppix, back when storage was scarce and expensive -- I couldn't afford a backup drive for the family PC (which I ended up being admin for despite violating COPPA every time I asked for technical advice online). So I was scared to repartition or anything...

Actually, I'd suggest guiding her through burning one of her own.

Then let her decide if she wants to keep Windows on the machine or install it.

The process of obtaining an ISO, burning it, and booting it will teach her a lot about the hardware involved.