This PC is wonderful. Shipping was quick, the unit is in great condition cosmetically. HOWEVER: when I powered it up the fan sounded like an old reel projector and i received a BIOS error message that the CPU fan was undetectable. It wasn't an airflow noise, it was a mechanical noise so loud you could hear it from down the hall. I popped the cover off and saw that the fan plate was almost imperceptibly depressed in the middle. I detached the fan from the plate (keeping it plugged in) and gently pressed it back into shape over my knee. Screwed it back in, plugged everything back in and booted up. The fan is now nearly silent; I can hear that it is working, but I don't feel like there's a silent movie projector in the room. The fan error is also gone from startup and there's no additional fan errors in the BIOS log.
I still got a screaming deal on this $1400 PC, this is my third purchase from BackMarket and I'll for sure be back. Since I don't know what caused the bent plate and I know they would have given me my money back if I asked, I'm not taking away any stars. But be aware, while looking around online, fan noise seems to be a common complaint for these units.