So my computer had windows 8.1 and for some reason I decided to go back to Windows 7 Home Premium x64. My cousin gave me an ISO and product keys from his University, and I created a bootable USB and DVD. For the DVD, I couldn't boot it said something like " device not Available strike F1". The USB, the installation got to 26% then told me that some file was missing (0x80070216). By this time the HDD with the ISO had formatted.
So now, I am really confused of what to do.
I have a Dell Optiplex 760 with Intel Core 2 Duo E7300 @ 2.66 GHZ. I have 4GB RAM (2x2) with onboard graphics. I have access to my laptop.
I was thinking of installing UBUNTU and then creating a bootable USB from there, and actually I'll try that now.
PLEASE HELP ME!!!
Thanks to anyone who replies.