help! factory reset desktop

I bought a used hp pavilion and I'm having trouble factory reseting it. for some reason I can't connect the internet. I know it has to do with the computer because I spent hours on the phone with my Internet company. I have an hp laptop so I know how to reset it I've done it on my laptop. this computer won't let me back up any files so that I can reset it. I don't know what to do. it dose not have recovery manager and when I try to hit f11 from power on it does not work because It won't let me make a disk to back it up.