I accidentally formatted my hard drives while I was formatting my computer.

SATA : seagate barracuda7200.10 320Gbytes

I don't know how it work and I don't know basics on my computer :pYour post is unclear. You don't format a computer, you format a hard drive - so it sounds as though you did want to perform a format. And it is virtually impossible to format your system drive accidentally - you have to verify / approve the command multiple TIMES before the system will do it. Please explain exactly what you did IN DETAIL and explain what it is you want to do now.I wanted to formate my computer, like I just bought it. So I used a USB key that I changed into a BOOTABLE device which I changed into my BIOS settings, in a part of the format windows ASKED me which hard drive I wanted to delete and I SELECTED them all by accident and as I remember one had the description named "System" after I changed the page my computer restarted and I kept getting stuck at the boot page, I removed my SATA and it started normally and than it freeze. I'm stuck there:/ALSO I don't have a second Pc.It's still not completely clear, but if I understand what you did you'll need to reinstall the OS. Boot to a Windows disc and start the installation procedure.