What model laptop is it? That might help determine. You might want to note that code down from BIOS.
I haven't had to deal with anything like that thankfully...what a mess. At least it sounds like you don't have any data on there. Of course, the real issue is getting a valid Windows install working for free, as the laptop came with one. But it sounds like they messed that all up already?
In which case I think the nuke from orbit and wipe it all and cross your fingers approach is the way to go. (disclaimer: I'm not buying a copy if Windows if it doesn't work for you) ;)
I looked up info on Thurrott's site, he's been going through some current examples of this sort of thing.
https://www.thurrott.com/windows/100...-media-legally https://www.thurrott.com/tag/clean-pc/