I'll try that, it's actually the opposite, it has an uefi switch in the bios since it's so old it probably was the standard to use legacy boot, guessing by the CPU (core 2 duo, idk what model though) it's probably a 2007/08 prebuilt (by the weird PSU)
It would make sense that it would be a problem with windows if it didn't have the uefi setting on, but it still doesn't explain the "Ubuntu success" message I got instead (and that was the case when the Linux drive was completely disconnected )
Will reply after I try it out, if it doesn't work I'll try the CMOS instead, if that doesn't work either then I guess I fucked up my computer beyond repair