Trying to repair the computer by pressing F8 and Repair Your Computer was the first thing I did, but the window itself never appears, only the background and the arrow.
I had a USB flash with Windows 7 but I tried to look for it yesterday but I didn't find it.
Ill go buy a repair disc if it's not too expensive or Ill just borrow one from someone.
EDIT: never mind, I stood up from the chair and there, right under my bad, the USB flash was lying there

Just gonna fix BIOS settings and try