First, let me say that I hate white grubs. Not only for the damage they cause but also for the damage caused by the skunks, armadillos, moles and raccoons that dig up my yard searching for these tasty ...
It's probably Windows setting your UEFI (aka what used to be called BIOS) to boot from the Windows bootloader partition instead of Grub. It's probably still there if you set the right partition in the ...