Windows8 Laptop 17R

I started running the program to reset laptop back to factory setting cause I m going to send back to dell already have paper work set up to do that with Dell yesterday what I wanted to do was get all my personel information out of the computer before I sent it back it is taking for ever 2hrs up to 32 % only my Q is can I stop it or keep it running the way it is going and what happens next what do I have to do..Thank you