Possible virus downloaded in PC? Any explanation for issues I encountered?

My cousin had encountered issues where his PC would ask to choose an OS to boot into which was strange as I only installed windows 11 into it. From there it began to not detect any bootable devices.

I go to check it out and enounter the same issues, even after changing the boot priority (the only storage, a HDD, was still showing in the BIOS). I am unable to even boot into an Ubuntu image on a USB (crashes when it does a "file check" or something to that effect).

Suspecting the HDD, less than a year old, may be damaged I connect it to my rig (dumb mistake in hindsight), and I am able to view files in the hdd with no issues, several times. I assume then that the HDD is likely working and my cousin either downloaded something malicious or made a change to his system to damage it.

I setup a windows 11 image, and connect to via usb to his system where I reinstall windows. Even after successfully "installing" windows 11, i kept getting a no bootable device error. I was finally able to boot into an Ubuntu image on a USB, and still view the HDD, so I reinstalled linux with no issues, after which i was finally able to reinstall windows 11 with no issues.

I'm curious if this could have been a virus that cause these issues? (do any viruses cause similar issues?) If its more likely he did something wrong to the PC (he's not tech savvy) or potentially something else?