When my 2012 mbp went down with a bad ram stick, I installed Windows 8.1 on a bootcamp partition on my wife's 2010 mbp. I got my laptop working, not longer needed to borrow hers and attempted to remove the bootcamp partition. It is gone but when ever she reboots, she has to remember to hold the option key or she automatically boots to a black screen. I assume something didn't get properly uninstalled and its attempting to load Windows bios but it doesn't exist. Is there a way to fix this? There is no time machine or back up pre bootcamp installation to restore to.
I would Recommend installing windows 10 only and getting rid of the mac partition completely. There are tons of online tutorials on how to do it. BUT if you want to use the partition and have that be the default when you hit the option key to choose your startup disk, HOLD CONTROL before you select it that you’ll notice that upward-pointing arrow—the one that points to the selected disk—will change into a circular arrow instead, indicating that the chosen disk will not only be used to start your Mac this time, but that it will also become the default boot disk.