Aurora R13, Pin won't work anymore?

I messed up the PC (still don't know how haha) when she was still but a child (I'd had it for around 3 months). A dell guy came and I think he reset the motherboard but I'm not entirely sure. I had to reset the pin so I did but now it only works for PC login. So I can login to use my PC, but I can't download anything because it needs the pin to "allow apps to make changes to device". I've reset the pin loads of times and restarted the PC but it just won't work. Any ideas?